• As noted in the Rig Veda, written in 4500 BC, in ancient India aromatherapy existed in correlation with Ayurveda. The use of aromatic plants & plant parts for treatment & cure made a major section of Ayurvedic treatments according to the foundational texts of Ayurveda, Charaka Samhita & Sushruta Samhita.
• When smoothed on the skin, added to a bath, or inhaled in the form of steam, these aromatic ‘essential oils’ were believed to ease tensions, heal wounds and revitalise the body.
• Today, this practice, called aromatherapy, is gaining some acceptance among Western doctors as a way to use the senses to benefit health.
• There is even a smattering of evidence to support the value of using aromatic oils to help the immune system fight a variety of ailments.
• For example, tea tree oil — an antiseptic discovered by Aboriginal Australians — was found to make white blood cells more active.
• And inhaling lavender oil was shown to be more effective for insomnia than a placebo.
• Aromatherapy has gained quite a bit of attention in recent years. Aromatherapy products, once somewhat exotic, have now sprung up on the shelves of even grocery store aisles. Aromatherapy candles, bath products, essential oils, and other products are now widely available and have been touted as effective in soothing babies, relieving stress and promoting healthy living. But does aromatherapy live up to the claims?
• Aromatherapy is an alternative way of living which runs deep through our history and is a holistic therapy as well as the art and science of utilizing naturally extracted aromatic essences from plants to balance, harmonize and promote the health of body, mind, and soul. This alternate therapy has also proved to be helpful for cancer patients, especially at the recovering stage.
• Aromatherapy means healing through the sense of smell where we use essential oils derived a plant’s leaves, flowers, stalks, barks, rind or roots which contain the prana or life force of the plant to benefit our body and mind. Essential oils work on our emotions and have the capacity to alter our moods and are used to promote the well-being of a person. The oils deal with memory and psychological issues related to our mind such as depression, calming, anxiety, dealing with high blood pressure, improving memory and hypertension, etc in the cancer patients and survivors.
• Aromatherapy is a powerful science that should be used consciously to harmonize the mind, body, emotions and the soul and it can become a way of life. Aromatherapy seeks to unify physiological, psychological and spiritual processes to enhance an individual’s innate healing process.
  When we talk about cancer and its recovery, it is to be understood that the lifestyle, diet, emotions play a major role. After being cured, the survivor when goes back into the world, the environment around him/her should be positive, worry-free and enlightening which can help them to feel happy, normal and encouraged. During such illness, our body and mind suffer a bit too much with both physical and mental stress. The condition of trauma leaves its impact for a long time and to undo the effect, one needs to be calm and should accept the healing that is being offered to the body to be at peace with the present and future.
  Secondly, the survivor needs to be happy. The gratitude that develops in the heart after being cured and healed will work as a catalyst in the healing process.
• Happiness is indeed the best medicine and along with Aromatherapy, it can be helpful to promote a speedy recovery. Light diffusers around the recovering person and add 1 drop of their favourite fragrance. The aroma will cheer them up and help them to cope up with the emotional struggle as well. Here are some oils that can help with:

-Headache: Peppermint
-Respiratory infection: Eucalyptus
-Anxiety relief: Rose
-Indigestion relief: Peppermint
-Relaxation: Lavender

• Cancer treatment follows chemotherapy and radiation therapy which can cause stress to the recovering person. Henna, with its chilling effect, can help them to calm down and relaxes the head muscles. Use it on hands and feet while undergoing chemo.
• Cancer treatments sometimes have adverse effects on the skin in different ways. It makes the skin brittle, dry and distressed. You can use Soda bi-carbonate with a drop of lavender can help the rough, patchy and dry skin during the procedures.
• For aches and pains, use Epsom salt with rose essential oil and give hot compresses in the affected areas. You can add Epsom salt with drops of lavender into hot water and put your feet in it to relax the tensed nerves and let go off the pain.
  Chamomile oil and tea is also helpful to calm down.
• Different ways to use aromatherapy
  -Place a few drops of your favourite essential oil in a diffuser to allow a soothing fragrance to fill the room.
  -Sprinkle 2–3 drops of oil in your bath.
  -Sprinkle 1 drop of oil on a tissue or a handkerchief, and hold it up to your nose. Keeping your eyes closed to avoid irritation, take 2–3 deep breaths through the nose.
  -Place 2–3 drops of oil in a 4-ounce spray bottle of water. Shake the bottle and then spray fragrance around a room.
• Aromatherapy is a holistic healing treatment that uses natural plant extracts to promote health and well-being. Sometimes it’s called essential oil therapy. Aromatherapy uses aromatic essential oils medicinally to improve the health of the body, mind, and spirit. It enhances both physical and emotional health.
• Aromatherapy is thought of as both an art and a science. Recently, aromatherapy has gained more recognition in the fields of science and medicine.

How long has aromatherapy been around?

• Humans have used aromatherapy for thousands of years. Ancient cultures in China, India, Egypt, and elsewhere incorporated aromatic plant components in resins, balms, and oils. These natural substances were used for medical and religious purposes. They were known to have both physical and psychological benefits.
• Essential oils distillation is attributed to the Persians in the 10th century, though the practice may have been in use for a long time prior to this. Information about essential oil distillation was published in the 16th century in Germany. French physicians in the 19th century recognized the potential of essential oils in treating disease.
• Medical doctors became more established in the 19th century and focused on using chemical drugs. However, the French and German doctors still recognized the role of natural botanicals in treating illness.
• The term “aromatherapy” was coined by a French perfumer and chemist René-Maurice Gattefossé in a book he wrote on the topic that was published in 1937. He had previously discovered the healing potential of lavender in treating burns. The book discusses the use of essential oils in treating medical conditions.

How does aromatherapy treatment work?

Aromatherapy works through the sense of smell and skin absorption using products such as these:

• diffusers
• aromatic spritzers
• inhalers
• bathing salts
• body oils, creams, or lotions for massage or topical application
• facial steamers
• hot and cold compresses
• clay masks

You can use these alone or in any combination

• There are nearly one hundred types of essential oils available. Generally, people use the most popular oils.
• Essential oils are available online, in health food stores, and in some regular supermarkets. It’s important to buy from a reputable producer since the oils aren’t regulated by the FDA. This ensures you’re buying a quality product that is 100 percent natural. It shouldn’t contain any additives or synthetic ingredients. Check out these essential oils available on Amazon.
• Each essential oil has an array of unique healing properties, uses, and effects. Combining essential oils to create a synergistic blend creates even more benefits.

Aromatherapy benefits

Aromatherapy has an array of benefits. It’s said to:

• manage pain
• improve sleep quality
• reduce stress, agitation, and anxiety
• soothe sore joints
• treat headaches and migraines
• alleviate side effects of chemotherapy
• ease discomforts of labor
• fight bacteria, virus, or fungus
• improve digestion
• improve hospice and palliative care
• boost immunity

Unproven claims

• Scientific evidence for aromatherapy is considered to be limited in some areas. Research to support the use of aromatherapy in treating Alzheimer’s disease, Parkinson’s disease, and heart disease is lacking.

Conditions it may treat

Aromatherapy has the potential to treat many conditions, including:

• asthma
• insomnia
• fatigue
• depression
• inflammation
• peripheral neuropathy
• menstrual issues
• alopecia
• cancer
• erectile dysfunction
• arthritis
• menopause

Most popular aromatherapy oils

According to the National Association for Holistic Aromatherapy, the most popular essential oils are:

• clary sage
• cypress
• eucalyptus
• fennel
• geranium
• ginger
• helichrysum
• lavender
• lemon
• lemongrass
• mandarin
• neroli
• patchouli
• peppermint
• Roman chamomile
• rose
• rosemary
• tea tree
• vetiver
• ylang ylang

You can use essential oils in any number of ways. For example, add them to body lotions or carrier oils, and then apply them topically. Try enhancing a facial toner, shampoo, or conditioner with essential oils. Or incorporate them into liquid soap, toothpaste, or mouthwash. You can also diffuse or spritz the oils throughout a room or pour them into a bath.

Choosing a provider

• You may wish to meet with a certified aromatherapist, especially when you’re first getting started with aromatherapy or if you have specific issues you’d like to address. You can find an aromatherapist by using an online directory. Or ask at a spa or yoga studio.
• During a consultation with an aromatherapist, you’ll answer questions and talk about your lifestyle and health. Together, you can come up with an individual treatment plan to meet your goals and manage your symptoms. You may have a few sessions with your aromatherapist, or you could decide to have ongoing sessions for a longer period of time.
• Since aromatherapy is a complementary therapy, you should talk to your doctor before starting your sessions. That way your essential oil therapy can be tailored to work together with any medical care or treatment you’re receiving.
• There’s plenty of information available online and in books if you wish to treat yourself at home. There are also courses you can take to learn more about aromatherapy.
• Consultations with an aromatherapist will vary depending on several factors, including where you live. You can expect to pay up to $100 for an initial consultation and up to $50 for follow-up consultations.

Side effects

• Most essential oils are safe to use. But there are some precautions you should take when using them, as well as side effects you should be aware of, especially if you take any prescription medications.
• Don’t apply essential oils directly to your skin. Always use a carrier oil to dilute the oils. Remember to do a skin patch test before using essential oils. Since citrus essential oils may make your skin more sensitive to the sun, these oils should be avoided if you’ll be exposed to sunlight.
• Children and women who are pregnant or breastfeeding should use essential oils with caution and under the supervision of a doctor. You should avoid some oils and never swallow essential oils.

Side effects of using essential oils include:

• rashes
• asthma attacks
• headaches
• allergic reactions
• skin irritation
• nausea

Use essential oils with caution if you have:

• hay fever
• asthma
• epilepsy
• high blood pressure
• eczema
• psoriasis

Takeaway

• As you explore the uses of essential oils, pay attention to how the different oils and methods of use affect you.
• Always talk to your doctor before starting any aromatherapy treatment. Remember that aromatherapy is meant to be a complementary therapy. It’s not meant to replace any doctor-approved treatment plan.

Important things to consider

• Make sure you’re using pure essential oil and not any blends.
• Pregnant women and children should avoid inhaling essential oils and rubbing it on their skins.
• Do not blend a lot of aromas, and always check with your doctor before trying Aromatherapy or using essential oils.
• After a lot of medication and chemotherapy the skin tends to become really sensitive and therefore before using any essential oil, do a patch test.

How to do a patch test

• Apply a few drops of essential oil on a portion of your hand. Leave it for 24 hours. If there is any skin reaction such as a rash, soreness or irritation, do not continue to use the oil.
• Aromatherapy is used by patients with cancer as a supportive therapy to heal their body, mind, and soul. The therapeutic use of essential oils in Aromatherapy has been helping cancer patients in improving their physical, emotional and spiritual well-being.

Aromatherapy & Essential Oils for Stress Relief

• If you need improvement in health problems from anxiety to poor sleep, you may want to consider aromatherapy. In this kind of treatment, you use extracts from plants called essential oils, by either breathing them through your nose or putting them on your skin. Some people put the oils on their skin when they get a massage or take a bath.

What Are Essential Oils?

• Essential oils are made from flower, herb, and tree parts, like bark, roots, peels, and petals. The cells that give a plant its fragrant smell are its “essence.” When an essence is extracted from a plant, it becomes an essential oil.
• It takes a lot of plant product to make essential oils. More than 200 pounds of lavender flowers are used to make just 1 pound of lavender essential oil.
• Not all products made with plant essence are essential oils. True essential oils aren’t blended with other chemicals or fragrances. They’re made using a specific process that doesn’t change the chemistry of the plant.
• Lemon, chamomile, lavender, cedarwood, and bergamot are a few of the essential oils used regularly in aromatherapy.

How Aromatherapy Works

• Experts think aromatherapy activates areas in your nose called smell receptors, which send messages through your nervous system to your brain.
• The oils may activate certain areas of your brain, like your limbic system, which plays a role in your emotions. They could also have an impact on your hypothalamus, which may respond to the oil by creating feel-good brain chemicals like serotonin.
• Some experts think that when you put essential oils on your skin, they cause a response in your skin and other parts of your body, like your joints.

What Is Aromatherapy Used For?

You shouldn’t use aromatherapy instead of your regular medical treatment. But for some conditions, research shows that aromatherapy can have health benefits. It may:

• Ease stress, anxiety, and depression
• Boost feelings of relaxation
• Improve sleep
• Help improve quality of life for people with long-term health problems like dementia
• Ease certain types of pain, including pain from kidney stones and osteoarthritis of the knee
• Fight bacteria when you put them on your skin
• Ease some of the side effects of cancer treatment, like nausea and pain

Is It Safe?

• Aromatherapy is generally safe. Essential oils can cause side effects, though. Some can irritate your eyes, skin, or mucous membranes in your nose. They can also cause mild allergic reactions.
• If you drink some essential oils they can hurt your kidneys or liver. It’s rare that people take essential oils by mouth, and you shouldn’t do it unless your doctor says it’s OK.
• If you’re new to aromatherapy, work with an aromatherapist or your doctor. And keep in mind that essential oils aren’t regulated by the FDA, which means that unlike drugs, the agency doesn’t check to see if they’re safe or work the way they’re supposed to.

Relatively little research is available on aromatherapy. While more studies are being done, it’s not as ‘proven’ as some other stress relievers. However, while further studies are needed, many studies have already shown aromatherapy’s benefits. Of the research that has been done to date, here are some of the findings:

• Preliminary research shows that aromatherapy can alter brain waves and behavior.
• Aromatherapy can reduce the perception of stress, increase contentment, and decrease levels of cortisol, the “stress hormone.”
• Lavender aromatherapy has indeed been shown to reduce crying in infants and promote sleep in infants and adults.
• Different aromatherapy scents bring different effects on people.
• One study showed that aromatherapy massage can have some beneficial effects on anxiety and depression.
• Massage with aromatherapy provides stronger and more continuous relief from fatigue-especially mental fatigue-than massage alone.

As a Stress Relief Tool

• While aromatherapy isn’t the magic ‘cure-all’ that it’s sometimes made out to be, it does appear to have proven effects as a stress reliever. Aromatherapy is a nice tool for stress relief because it has few (if any) known side effects, can be used passively (you can fill the room with scent while you attend to other activities, relieving stress in the process), and can be easily combined with other stress relievers (like massage or meditation, for example), for increased stress relief. Aromatherapy products are also widely available, making aromatherapy a convenient option.
• Aromatherapy can be convenient, especially for busy people who need something quick. Here are some ideas for aromatherapy use:
• Candles are great for aromatherapy. Lighting a candle is probably one of the simplest ways to scent up a room and create a nice feel, so get some aromatherapy candles and let them burn. The candles, like incense, can also be used to create a more soothing atmosphere, or as a focal point for meditation. However, they may be more practical than some incense because they don’t give off as much smoke.
• Aromatherapy diffusers take essential oils and evaporate them through the air. This can be with the help of a candle or with batteries if you want to avoid the fire. Diffusers are great because they spread the scent quite effectively. The battery-run ones can be safer than candles-no open fire involved. This is another convenient method of creating a soothing atmosphere, and many of them look really nice as well, adding to the soothing vibe you should create anyway.

Body Products

• Aromatherapy body products are great because they create a scent that follows you but can’t necessarily be smelled by others (unless they’re very close, in which case they probably won’t mind). You can rub aromatherapy lotion all over your skin, or dab a few drops of skin-safe essential oils on pulse points and enjoy the scent for hours.
• Aromatherapy combined with massage carried greater benefits than either strategy by itself. If you’re lucky enough to have someone who will trade aromatherapy massages with you, this can be a wonderful and cheap strategy for stress relief. If not, paying for a massage from a professional can be worth the money.

Meditation

• Aromatherapy can enhance the relaxation benefits of meditation, providing a focal point (as with incense meditation), and offering the passive stress relief benefits of aromatherapy. Even a five-minute meditation can bring benefits.

Aroma Therapy & Immune System

• During the winter months, our bodies can benefit from a little bit of extra attention. The immune system is one of the main engines safeguarding us, so we are happy and healthy.
• But why are we more vulnerable in winter? Research from Yale showed that the reason why our immune system is at a disadvantage during the winter is that the cold weakens the nose’s first line of immune defence. The ability of immune cells to perform apoptosis (self-destruction to prevent the spread of a virus to other cells) is compromised, leaving the immune cells in a disadvantage from invading germs .
• Moreover, the lack of vitamin D, due to less exposure to the sun, also plays an important factor. Vitamin D has numerous health benefits but is essential when it comes to a well-functioning immune system. Our killer cells, or T-cells (cells actively searching for harmful pathogens to destroy in the bloodstream), need vitamin D to activate. If there’s a shortage of Vitamin D, the effectiveness of the adaptive immune system is suppressed.
• Essential oils’ therapeutic properties can help strengthen the immune system. This month, we’ll dive deeper into what essential oils can offer in supporting our bodies to conquer cold drafts and grey, snowy days!

Factors That Influence The Strength Of The Immune System

• Various factors determine how well our defence mechanism is performing. No matter how healthily you live, it’s only natural that the immune system is weakened at some point. Factors such as stress, sleep, diet, and exercise influence the vitality of your immune system. Following a nutritious diet with 7 to 8 hours of sleep and enough exercise should get you at least on the right track.

How The Immune System Works

• The immune system is our first defence protecting us from viruses, diseases, and pathogens entering our body. If any harmful organisms have found its way into our bloodstream, the antibodies attack the intruders and clear the invaders from our system.
• The immune system activates when it comes across something that it doesn’t recognize as his own. The first line of defence is the non-specific immune system, or innate, and acts as general protection to fight off microbes entering through the skin mucous membranes. The second defence system is the specific, or adaptive, immune system where it detects, attacks, and neutralises harmful pathogens.
• Pathogens (or germs) are, in principle, any organism that can produce disease. They carry an antigen, a type of protein found on the surface of the pathogen, that binds to a specific B-cell antigen receptor or antigen-specific antibody. The immune system is programmed to target antigens. After a lymphocyte (a type of white blood cell) recognises the antigen, it produces antibodies specific to that antigen. The antibodies then attack the pathogen by locking into the unique shape of the antigen. After the pathogen is destroyed, it’s absorbed by macrophages (a process called phagocytosis).
• At the risk of sounding cliche, prevention is the key to never being in a position where you’d need curing. However, we are all guilty at times of not consciously implementing measures to protect our family from diseases.
• You should know, however, that the time to build up your immunity against common illnesses is before you catch anything, not when you first notice the symptoms.

How Essential Oils Fortify Our Immune System

• Essential oils contain compounds that have pharmacological properties. These compounds, including carbohydrates, ethers, alcohols, aldehydes, and ketones, are the reason essential oils have a specific fragrance and biological properties for medicinal purposes .
• They can either fortify the immune system or eliminate harmful bacteria and viruses. While all essential oils contain antibacterial, antiviral, and antiseptic properties to some extent, some essential oils have more of one than the other. Depending on their characteristics, essential oils can fight viruses, purify the air, alleviate flu-like symptoms, and bring comfort during illness.
• Besides the biological factors, essential oils also provide a psychological benefit. Essential oils derived from herbs such as lavender and rosemary promote relaxation by reducing stress levels (cortisol). The hormone cortisol lowers the immune system’s defence mechanisms, by reducing the levels of lymphocytes and compromising the growth of T-cells. Aromatherapy can help in relieving tension and stress. Research shows that inhaling lavender and rosemary essential oils reduces cortisol levels, thus boosting the immune system .

Best Essential Oils For The Immune System

• Although essential oils can have beneficial effects all year round, we selected these five for their particular immune system qualities. Essential oils can be used in different ways, but here, we focus on inhalation.

Eucalyptus Globulus — spiritual grounding, purification, removing blockages and negative energies

• Eucalyptus Globulus is well-known for its refreshing fragrance, cleansing properties, and support in respiratory illness relief. It contains a high percentage in 1,8-cineole, generally between 60–90%. After inhalation, research shows that it supports the health and functioning of monocytes and the production of T-cells.
• Eucalyptus oil also has antibacterial effects on infectious bacteria in the upper respiratory tract, including those causing influenza and strep. Its aromas also open the respiratory tract and decongest sinuses, and soothes painful coughs. With its strong antiseptic and anti-inflammatory properties, it strengthens the immune system and invigorates the body.
• Of course, this list won’t be at all complete without mentioning eucalyptus essential oil. It is more commonly employed as a remedy after colds or flu has already set in, but our theme here is prevention, and eucalyptus essential oil may also be employed to that end just as effectively.
• Eucalyptus essential oil’s applications for helping treat cold and flu symptoms are wide and well-known. Commonly found as one of the main ingredients in over-the-counter drugs and remedies, it could, among other things, help decongest the chest and clogged sinuses, expel stubborn mucus, and relieve the various aches and pains involved with the said illnesses.
• As a preventative measure, meanwhile, eucalyptus essential oil can help improve the immune system’s function by promoting “innate cell-mediated immune response,” according to this study. In simple terms, we could take this to mean that eucalyptus oil stimulates the immune system on the cellular level.
• In particular, it induces the activation of “phagocytes,” which are the body’s main attackers when harmful invaders get in. The more of these soldiers we have, the better our body’s chances of not getting sick even if we do get infected.
• Its head-clearing aroma is a key ingredient in Vicks VapoRub.
• The claim: A powerful antiseptic and healing agent, it is also renowned as a treatment for respiratory complaints.
• For best results: Mix with a carrier oil and massage into the chest, or add 3 drops to the dust bag of your vacuum cleaner to repel dust mites and freshen the air throughout your home.
• Nontoxic externally, but taken internally it is very toxic — 3.5 ml is usually fatal.
• With its powerful natural antiseptic, disinfectant and cleaning properties, eucalyptus oil can be put to work in every room of the house.

Lemon — Promotes white blood cell production, stabilizes mood, and improves blood circulation

• Lemon essential oil a serious mood uplifter. Research consistently shows that it alleviates symptoms of anxiety and depression.
• Additionally, lemon essential oil offers strong antibacterial and antioxidant qualities that do wonders for the immune system and your energy levels. So is lemon essential oil also associated with enhanced production of lymphocytes, the body’s main type of immune cells.
• Now, what is a list of immunity-boosting essential oils without lemon in it? Would such a list even exist?
• It is common knowledge that lemon fruit has noteworthy immunity-boosting properties. Its essential oil would, of course, be no different.
• Like several other citrus essential oils, lemon essential oil is high in d-limonene content, which is a crucial compound for the promotion of white blood cell production among many other immunity-related things.
• Science has been doing its part to see whether or not essential oils can really be beneficial to human beings’ overall health — not just of the body but also of the mind.
• Thus far, the studies have been giving us hopeful results, and most of these can be taken as mere confirmation of what essential oils users have already known, not just for the last few decades but for the last few millennia. To this end, lemon has been hailed as possibly the most powerful essential oil when it comes to fighting all sorts of microbes.
• Whether it’s before these microbes enter your system or after, lemon essential oil can be relied upon to help you defend against them.
• And similar to another citrus essential oil on this list, lemon can also serve as a mood stabilizer which could possibly lead to an improved functioning of the body’s various systems. Better quality of rest and sleep along with a healthier appetite may just prove to be enough to boost your immune system up, but lemon essential oil’s other properties would be on hand in the off chance that it isn’t.

Rosemary

• Rosemary essential oil has potent antibacterial properties that help protect your body. Similar to eucalyptus oil, rosemary essential oil has a positive effect on protecting you from airway illnesses. Because of its high percentage of 1,8-cineole, has an anti-inflammatory effect on airway illnesses .
• On top of that, the oil has fortifying qualities boosting the immune system because of its psychological benefits. Research shows the feel-good properties of rosemary; reducing cortisol-levels and so increasing the strength of your immune system.

Tea tree — disinfects air and surfaces, fights various types of infection, and relieves pain

• Tea tree essential oil fights infections and inhibits harmful bacteria. With potent antibacterial and antifungal qualities due to high levels of alpha-sabine and anti-sceptic qualities because of terpinenen-4-ol, tea tree essential oil is a notable immune booster. For example, research shows that its significantly suppressed proteins associated with an inflammatory response.
• Having antibacterial, antifungal, and antiviral properties, tea tree essential oil can effectively act as your first line of defense against many common pathogens. Unlike most essential oils that share these properties, tea tree can actually be considered as an immune system stimulant rather than simply a support.
• If it’s diffused regularly in your home or office spaces, it can also serve as an air disinfectant, killing many types of sickness-causing germs floating around. If employed as a surface cleaner, you can expect the same benefit.
• These amazing effects have been substantiated. When tested for possible effects on many virus strains, tea tree essential oil has been found to be significantly effective against influenza strains.
• Of course, its uses aren’t limited to just air and surfaces.
• Regular inhalation of its scent can also give the human body the same defensive effects. Even topical application can work just as well. If one or two diluted drops are rubbed in your pulse points, tea tree essential oil could serve as a shield against viruses and bacteria that you can carry with you as you go about your day.
• Products made with this plant have a menthol-citrus scent.
• The claim: Widely recognised as a powerful tool against a variety of harmful bacteria, viruses, fungi, moulds and parasites.
• For best results: To ease skin infections and inflammation, add 3–5 drops to bathwater.
• For relief of respiratory ailments, add 2 drops to a bowl of steaming water and inhale the vapour for five minutes.

Clove

• Clove essential oil is one of the most robust antibacterial essential oils. Its high percentage of eugenol, generally between 70–76%, supports strong antimicrobial and antifungal properties that cleanse harmful molecules from the air. It’s suggested that clove essential oil promotes the regeneration of specific cells and protein associated with the immune system and inflammation.

Fir — expression of gratitude, relieves stress and anxieties, alleviates depression, balancing the sacral and solar plexus chakras

• Here’s another essential oil that has more than one use when it comes to helping you ward against illnesses.
• First, fir essential oil can be used as a surface and air disinfectant, killing germs before they have the chance to breed and spread.
• Second, it is another immune system stimulant, boosting your body’s defenses to help keep you from catching cold or flu bugs.
• Third, if it’s far too late for immunity boosters and you’re already feeling the first symptoms of sickness, fir essential oil can also be employed to help you stop it on its tracks and facilitate a speedier recovery.
• Most modern people don’t often hear of essential oil from fir mentioned in this regard, but it has a long history with many old cultures that have used not just the oil but the tree’s various parts as medicine for their various ailments. Its needle-like leaves, for instance, are surprisingly high in vitamin C, and these have been traditionally made into tea.
• Similar to tea tree and to many other essential oils, fir essential oil has antibacterial, antifungal, and antiviral properties that all serve to help the body fight off all sorts of infections. If used preventatively, it can potentially stop infection from spreading throughout the body.
• Please note that fir essential oil is one of those not recommended for regular and/or long-term use as its high toxicity may accumulate and affect the body’s organs. It is not dangerous if used sparingly, and it is best employed as a sometime booster when flu season is coming, or as an air and surface disinfectant when someone in the house is already down with something, in order to keep the infection from spreading.

Bergamot — boosts holistic wellness, eliminates pathogens, and relaxes the muscles

• Bergamot essential oil can be characterized more as an immune system support rather than a stimulant, but that doesn’t make it any less effective in helping you fight illness-causing organisms before they can even land.
• One of the ways bergamot can be employed to this end is through inducing not just your body but also your mind to feel better in a general sense.
• As a highly effective mood booster, bergamot essential oil can help reduce feelings of stress, anxiety, and depression, which are just some factors that could cause your immune system to take a nosedive.
• It’s a fact, after all, that when you’re not feeling your best emotionally, it could translate physically. Some examples include an inability to get effective rest when you need it, a shortened or lengthened sleeping time with limited renewing quality, and a reduced appetite that lowers your body’s chances for getting the proper nutrition it needs to defend itself against invaders.
• All of these can be addressed in one fell swoop if you first work on regulating the emotional issues that are causing them, which is where bergamot essential oil can shine.
• That’s not all it’s good for, though. Bergamot also has a reputation not just for helping keep the body from getting sick but also for helping it recover from illnesses.
• When it gets into the system either through the skin or through the lungs, bergamot essential oil can encourage the production of more white blood cells, which is extremely necessary if the body is to have its immune system in good working order, either to renew itself or to keep the sickness from recurring.
• As a cherry on top of this already-attractive cake, a study has found that vapor diffusion of bergamot essential oil was highly effective in fighting the influenza virus after only ten minutes of exposure.
• If used in this manner with eucalyptus essential oil (which also had the same result) as well as with the others mentioned in this article, bergamot essential oil could prove to be an especially fine net that no virus could pass through.

Lemon Grass — Promotes nutrient absorption, shields against pollutants, and tones the nervous system

• Lemongrass essential oil is another all-in-one wonder that can be used for air and surface disinfecting, immunity boosting, and sickness busting.
• This essential oil doesn’t share lemon’s name for nothing. It contains a significant amount of limonene as one of its major components.
• Moreover, lemongrass essential oil doesn’t just have properties that can protect against bacterial, fungal, and viral infections — it is also a well-known fever remedy used in traditional medicines of the countries where lemongrass grows in abundance.
• Its role in improving the immune system involves helping the body absorb nutrients more efficiently, as one of its main functions is in improving the digestive system.
• See, it’s sometimes not enough to observe proper diet in order to protect against common and not-so-common illnesses, you also have to make sure your body is working optimally such that it can break down food and effectively disseminate its components throughout the body.
• We need to make sure that whatever we ingest can be converted into compounds we can benefit from.
• Finally, in the same study that tested much essential oil’s potency against viruses, lemongrass essential oil’s vapor diffusion was found to be effective at eliminating influenza virus after thirty minutes of exposure. This, along with its capacity to protect the nervous system from various modern-day pollutants, may serve to protect the body from many harmful elements that can bring its defenses down.

Cedarwood

• Most ‘cedarwood’ oil comes from juniper!
• The claim: North American Indians used this scent to treat respiratory infections and today it is believed to ease coughing and other cold and flu symptoms.
• It’s also an effective insect repellent.
• For best results: Inhale or use as a compress. Causes skin irritation in some people. May increase menstrual flow. Avoid if pregnant.
• Don’t put up with persistent coughs or sniffles.

Chamomile

• Pressed from daisy-like flowers, it has a fruity aroma.
• The claim: Known for its calming effects, it is thought to reduce inflammation and fight skin infections.
• For best results: Use topically or add 6–10 drops to running bathwater.
• Low toxicity makes it particularly safe, even for children.
• Natural doesn’t always equal safe when it comes to your body.

Clary Sage

• Distilled from the pale blue flowers of a plant that grows to about a metre in height.
• It is a close relative of the common sage, Salvia officinalis.
• The claim: Its antiseptic and astringent qualities help relieve skin inflammation, including acne.
• It is also used to ease tension headaches.
• For best results: Mix up to 5 drops in about 10 ml of water and heat over an aromatic oil burner.
• Do not use if drinking alcoholic beverages. Avoid if operating machinery or driving. Do not use during pregnancy.

Cypress

• Distilled from the cones of the cypress tree.
• The claim: This aroma is said to build emotional and mental resolve.
• Inhaling it may help relieve the symptoms of throat and respiratory infections.
• For best results: Place a few drops in a saucer of water and leave in a warm part of the house.
• May cause allergic reactions in susceptible people.
• Avoid if you suffer from high blood pressure.

Ginger

• A staple of Asian cuisine, ginger is used in Indian medicine to combat arthritis.
• The claim: Noted for its warming and decongestant properties, ginger also helps fight off colds and flu and reduces fever by inducing perspiration.
• For best results: Mix with a carrier oil and massage into the chest, inhale, or add 6 drops to running bathwater.
• May irritate the skin if applied undiluted.
• When your body feels out of whack, certain foods can help set you back on the right track. Ginger is one such food.

Lavender

• The oil is taken from the fresh, blue-mauve flower spikes.
• The claim: Alleviates stress and depression, induces sleep and relaxation and promotes circulation.
• For best results: Use topically or add 10 drops to bathwater. Sheets washed in water containing lavender oil may promote sleep.
• Nontoxic, but the scent may trigger nausea if too much is used.

Peppermint

• This plant is native to Europe and Asia.
• The claim: Relieves pain when applied externally to sore muscles.
• Also fights fever and helps to ease headaches and respiratory infections.
• For best results: Only a small amount of peppermint is required, whether used topically or in bathwater.
• Keep eyes closed when inhaling its scent and wash hands thoroughly after use.
• Keep away from the faces of small children; may cause wheezing or an involuntary gagging response.

HOW TO USE THESE OILS

Create your immune boost blend of these 5 oils:Recipe for 10ml = 200 drops

• Lemon 100 drops
• Eucalyptus globulus 60 drops
• Tea tree 25 drops
• Rosemary 10 drops
• Clove 5 drops

In an ultrasonic diffuser:

Step 1: Fill the water reservoir with water.
Step 2: Depending on the size of the room and your personal preference of fragrance intensity, you can add 5 to 10 drops of essential oil.

Step 3: Choose the duration of the mist and possibly the colour of the LED light.
Step 4: Enjoy all the benefits that nature has to offer.

Add one drop in a large bowl of hot water for a 5 min intense steam inhalation.

Caution

• Using aromatherapy to help your immune system, there are a few things that you should take into account:
• Its high concentration means that you should always dilute the oils if you bring them on the skin and don’t take them orally without professional guidance.
• Go for natural and pure oils to benefit from aromatherapy
• Do your research. Some essential oils are more potent than others and work differently.
• Consider the essential oil dosage and age of users. The amount of recommended drops for single use can vary across different types of essential oils. The age of the intended user is a factor as well, along with the manner you wish to apply it. Children and elderly people would need a lower dosage, and it is generally inadvisable to ingest essential oils, though it’s been known to be done in small amounts. But there’s a lot of accompanying dangers to this, so please check the recommended dosage for specific essential oils and the proper ways to use it by speaking to a qualified aromatherapy practitioner.
• Always dilute essential oils before applying them topically. Again, the recommended number of drops would vary per essential oil, but the standard for essential oils produced through the steam distillation method is one drop per one milliliter of carrier agent. Examples of effective and skin-friendly carrier agents include fractionated coconut oil, virgin or extra virgin olive oil, and other vegetable oils in general.
• Practice caution when handling cold-pressed essential oils. If you’re using a citrus essential oil that was made using the cold pressing method, you would generally need less than a drop to get an effect compared with steam-distilled essential oils. But because they are highly concentrated, potent, and acidic, greater caution would often need to be observed in their use. For instance, because they are photosensitive, exposure to sunlight after topical application is not recommended for at least twelve hours for the gentler citruses, and that length of time needs to be extended to twenty-four hours if more potent citruses like lime are used.
• Perform a skin patch test. But whether it’s cold-pressed or steam-distilled, always perform a patch test before any extensive skin application in order to check for allergic reactions or any other adverse effects. If there’s any irritation, either increase the essential oil’s dilution or stop using it topically altogether.
• Take extra note of whether a specific oil may be used long-term or only periodically. Some essential oils might prove toxic under prolonged exposure. For instance, the use of fir essential oil is recommended only for up to two weeks at a time. When diffusing essential oils, please also note that the recommended maximum length per session is one hour. Overexposure to essential oils may lead to effects such as headaches, nausea, and possibly emotional disturbances.
• If you’re pregnant, breastfeeding, suffering from conditions like epilepsy, or taking prescribed medication, please refrain from using essential oils. They commonly have one or more properties that may be harmful to your circumstances. Always consult your health provider’s advice before anything else.
• Store essential oils away from sunlight and keep them from children’s and pets’ reach.Majority of essential oils are not recommended for use in very young children, and some have been known to be harmful to animals. Avoid ingesting large amounts as essential oils can be toxic, and keep away from the eyes and other mucous membranes. In case of contact, flush with water, but if a large amount of undiluted essential oil spills on the skin, use carrier agents and not water to thin it out and clear it away.

HOW TO USE ESSENTIAL OILS TO BOOST IMMUNITY

• Whew! Despite how daunting those precautions we just covered may appear, their mention and observation are necessary for your safety.
• In this section, we’ll list the ways you could use these oils, divided by their possible uses as air and surface disinfectants and as stimulant and support for your body’s immunity.

1. AS AIR AND SURFACE DISINFECTANT

DIFFUSING

• In a majority of cases, even as simple a method as diffusion can prove enough to clear your air and your surfaces from bacteria and viruses that cause sickness.
• Simply add a few drops of any given essential oil in your diffuser and run it for an hour. You can choose to run it for longer than that, provided no one else would be in the room.
• For this purpose, the essential oils from tea tree, bergamot, or eucalyptus come highly recommended, but they may also be blended together and/or with lemongrass essential oil and lemon essential oil for maximum germ-killing effect.
• Fir essential oil may also be used as a potent preventive measure when cold and flu season is about to roll in, but not regularly, as was mentioned.
• When blending amounts for more than one use, it should be done in a thick and airtight light-filtering glass container to protect its volatile contents from degradation from both the air and the sun. Citrus essential oils are also known to be acidic and may eat their way to plastic or ordinary glass containers, rendering the essential oils unsafe for further use.

ALL-PURPOSE SPRAYER

When used as a sprayer, essential oils may work both as an air sanitizer and a general deodorizer, as well as an all-around surface disinfectant. To make one of your own, you’ll need:

• Distilled water — 1 ½ cups
• Rubbing alcohol — ¼ cup
• Tea tree essential oil — 20 drops
• Lemon essential oil — 8 drops
• Bottle with a fine mister

Instructions:

1. Blend the essential oils in a glass bottle until they’re evenly combined.
2. Add the blend to the bottle of combined alcohol and water, screw the cap tight, and shake well before every use.
3. Spray the solution on any space or surface that needs freshening and/or disinfecting.

Note: Other essential oils like fir, bergamot, and lemongrass may also be added (be sure to adjust the number of drops appropriately) and/or substituted.

2. AS IMMUNE SYSTEM STIMULANT AND SUPPORT

DIFFUSION

• Diffusion of any and all of the essential oils for boosting immunity can serve to protect you round the clock against common pathogens, and perhaps even not-so-common ones.
• To maximize this effect, blend your choice of these six (or, as we mentioned, all of them during critical times of the year) in a UV-filtering glass bottle, the number of drops depending on the size of the bottle you’re using.
• You may add an equal number of drops for each essential oil, or adjust depending on which specific effect you want more of.
• For example, if you want an ever-dependable mood-lifting effect while you load up on your microbe-fighting soldiers, use more of bergamot or lemon essential oil.
• Just remember that blending cold-pressed citrus essential oils with steam-distilled ones would require you to also adjust how you measure the drops from the resulting blend. Remember that a little goes a long way with the former kind, so if they’re in your blend, use it a bit more sparingly.
• You should also check if the diffuser you’re using is equipped to handle the citruses’ acidity as some have been known to cause damage.

TOPICAL APPLICATION

• For topical use, nearly everything said in the previous subsection applies, except that the oils, whether on their own or blended with the others, would also need to be mixed with an appropriate amount of carrier agent.
• Skin-friendly oils like coconut, olive, or jojoba could work very well to this end, but note once again that if you’re using cold-pressed citruses, more dilution would be required and sun-exposure for twelve to twenty-four hours must be avoided if it’s used on a large area of skin.
• Store your resulting blend in a sturdy and airtight glass bottle so it would keep for longer.
• For a handy way to carry it around and use it whenever it’s needed, you can also try storing it in a glass roller bottle. Apply your immunity-boosting blend in your pulse points or in the soles of your feet for quicker absorption.

STEAM INHALATION

• Sometimes, despite our best efforts, bacterial and viral infections get the better of us and we find ourselves dealing with the first signs of a cold or the flu before we know it. If this happens to you, you don’t have to panic.
• Simply employ a first aid treatment like steam inhalation to help get rid of the infection before it can get any more foothold.
• To do this, boil at least two cups of water, transfer it in a bowl, and add one to three drops of eucalyptus essential oil, fir essential oil, or a blend that contains both.
• Then, lean over the steaming bowl and use a towel to cover your head and shoulders, making sure the bowl is covered as well.
• Finally, inhale deeply and exhale through your mouth for ten minutes. Close your eyes if you find them stinging, and breathe in fresh outside air periodically if the heat gets to be too much. Perform this two to three times a day until your symptoms abate.

The Story of Aromatherapy in India.

• India is one of the oldest civilizations on the planet & Ayurveda, the ancient Indian medical system of healing, is probably the oldest & most well recorded ancient medical systems in the world. As noted in the Rig Veda, written in 4500 BC, in ancient India aromatherapy existed in correlation with Ayurveda. The use of aromatic plants & plant parts for treatment & cure made a major section of Ayurvedic treatments according to the foundational texts of Ayurveda, Charaka Samhita & Sushruta Samhita. Even till date, Ayurveda uses many aromatic plant parts for healing.
• Fragrant incense & scented flowers were an indispensable part of worship & religious rituals of this country since centuries. The natural aromas were thought to be related with spiritual upliftment & cleansing of the soul.

Aromatherapy in Ramayana

• There are also several mentions of application of aromatherapy in Indian ancient texts. One of the first recorded use of aromatherapy can be found in the Indian classic Ramayana, which gives a clear record of the war between Rama & Ravana. In the ‘Yuddha Kanda’ of Ramayana, Lakshmana, the younger brother of the king Rama, was injured by ‘Shakti Shel’ shot by Indrajit, the son of Ravana.

• Indrajit, a prince & a mighty fighter was empowered with many divyastras & he used one of his most powerful weapons on Lakshmana to seal the win of Ravana in the epic war. Lakshmana felt unconscious after being hit by the weapon & was near to death. When Lakshmana did not regain his consciousness even after hours, a worried Hanuman consulted the Royal Physician of Lanka, Sushena for advice.

• As the epic says, Sushena asked Hanuman to rush to the Dronagiri Hills to fetch some medicinal herbs or “booti” for treating Lakshmana & to heal his wounds. The four herbs that Sushena asked for the treatment included, Mruthasanjeevani, Vishalyakarani, Sandhanakarani and Savarnyakarani (Srimad Valmiki Ramayana, 74th chapter, Yuddakanda, Slokas 29–34).
• Hanuman rushed to the said hill but he was not able to identify the specific herbs with magical healing powers. Hence, he carried back the hill on his shoulder to the battle field. Finally, the aroma of Mruthasanjeevani was used for reviving Lakshmana from near death while the other herbs were used to treat his wounds & to heal the skin.

Aromatherapy and Buddha, the Gautama

• Clear mention of using floral aroma for treating Buddha in more than one occasions have been documented in the Buddhist scriptures, Tripitak, which makes it clear that during that period aromatherapy was a well-accepted way of treating ailments. When it comes to using aromatic plants for treatment during the era of Buddha, the name of the most accomplished physician of that time, Jivaka, should be mentioned.

• Jivaka was the grandson of Bimbisara & son of Abhaya, the prince of Rajagriha. He studied medicine in Taxasila for seven years under the reputed teacher Disapamok Achariya. His knowledge about medicinal herbs & medical skills earned him not only reputation but also praises from all the prestigious people of the society of the time.

• Jivaka being the most renowned physician of the time was called for treating Buddha who was suffering from “blocked intestine”. Buddha’s condition was so bad that Jivaka thought that he might not survive a strong purgative & he performed a massage on him & gave three handful of lotuses for inhaling the aroma (Vin.I,279).
• On another occasion, Buddha was injured by a stone splinter. Devdutta, Buddha’s cousin had hurled a rock at him & a splinter from that rock had injured Buddha’s foot seriously. The condition of the wound worsened over time as it was not treated immediately & finally Buddha had to be carried to Jivaka’s residence for treatment. Jivaka cleaned the wound with some plant extracts that had natural astringent properties (most probably, essential oils with anti-microbial properties) & bandaged it. Jivaka finally became a disciple of Buddha.

• Buddha himself is also known for suggesting different aromatic treatments to the monks for curing common ailments. Scriptures depict that he had suggested the monks suffering from bodily pains & aches to inhale the aroma of the cannabis leaves, after placing them in boiling water (Vin.I,204). Hence, the use of aromatic plant derived ingredients as well as the direct aroma of flowers for healing & cure was a tested & trusted treatment at that time.

Aromatherapy and king Ashoka

• The great Indian emperor Ashoka was seriously injured in the battle of Ujjain & most probably he was treated with aromatic herbal medicines, plant parts & scented baths that helped him to recover quickly. Ashoka was the son of the Mauryan emperor Bindusara. Though Ashoka had many elder male siblings, his intellect & prowess in warrior skills had made him the favourite of his grandfather, Chandragupta Maurya, the founder of the Mauryan dynasty.

• Growing popularity of Ashoka in the Mauryan army rang a bell for his elder brothers, as they thought Bindusara might prefer Ashoka as the next emperor. On persuasion by Susima, the eldest son of Bindusara, Ashoka was sent to exile but again called back to tackle the violent rebellion in Ujjain, where Ashoka was severely injured, though his generals succeeded to control the revolt.
• During this time Ashoka was kept & treated in hiding to ensure that his enemies could not find him. Ashoka’s treatment was done by the Buddhist monks & nuns. Devi, who later became Ashoka’s second or third wife was also one of the Buddhist ladies taking care of the king during that span.
• The treatments that cured Ashoka involved Buddhist treatments & medicines. In Buddhism, the use of aromatic plant parts & flowers as medicine for healing wounds was quite popular as it was often suggested by Buddha himself & also by his accomplished physician disciple Jivaka.
• Mention of elaborate bathing arrangements for King Ashoka, with scented flowers added to the water bath can also be found in the history. The flowers were used to make the bath more relaxing & energizing for the body & mind.

Aromatherapy during the Mughal era

• Babur, the founder of the Mughal dynasty in India, brought the Persian culture of perfume & use of fragrant plants with him during the XVI century. Bathing in water enriched with extracts of fragrant flowers like, rose, jasmine, champaka, Nargis etc. for complete body-mind relaxation was a common practice of the kings & queens of the era. It is also said that these luxurious baths were the real secret of the beauty of the women of the Mughal empire.
• Abul Fazal, the most famous historian during the Mughal dynasty, has mentioned in his records that Akbar had serious interest in making perfumes from flowers & these perfumes were mostly used for religious purposes & also to improve the atmosphere within the palace.

• A detailed description of the accidental discovery of rose essential oil by Asmat Begum, the mother of Jahangir’s wife Nur Jahan has been recorded in Tuzuki Jahangiri, the autobiography of the Mughal emperor.

• Jahangir (1605–1627) was the son of Akbar who inherited the thrown. According to the notes of the emperor, Asmat Begum was making rose water from rose petals most probably for use in skin care & also for the light, sweet & yet persisting aroma it offers, when she noticed “a thick mass on the surface of pots where hot rose water was poured from jugs”. She rubbed a single drop of that oily substance on her palm & realized that the whole room had become scented with the rich aroma of roses. Rose essential oil was later named as “Jahangir’s perfume” by Akbar’s wife Salima Sultan Begum, who also was the Empress.
• However, according to the written records of Mughal era available, the use of essential oils for curing illnesses was not popular at that time. The essential oils extracted from the fragrant flowers were mostly used for psychological benefits and also for religious purposes. Use of these rich oils in beauty & baths have also been mentioned.

Influence of Fragrances on Human Psychophysiological Activity

• The influence of fragrances such as perfumes and room fresheners on the psychophysiological activities of humans has been known for a long time, and its significance is gradually increasing in the medicinal and cosmetic industries. A fragrance consists of volatile chemicals with a molecular weight of less than 300 Da that humans perceive through the olfactory system. In humans, about 300 active olfactory receptor genes are devoted to detecting thousands of different fragrance molecules through a large family of olfactory receptors of a diverse protein sequence. The sense of smell plays an important role in the physiological effects of mood, stress, and working capacity. Electrophysiological studies have revealed that various fragrances affected spontaneous brain activities and cognitive functions, which are measured by an electroencephalograph (EEG). The EEG is a good temporal measure of responses in the central nervous system and it provides information about the physiological state of the brain both in health and disease. The EEG power spectrum is classified into different frequency bands such as delta (0.5–4 Hz), theta (4–8 Hz), alpha (8–13 Hz), beta (13–30 Hz) and gamma (30–50 Hz), and each band is correlated with different features of brain states. A quantitative EEG uses computer software to provide the topographic mapping of the brain activity in frontal, temporal, parietal and occipital brain regions. It is well known that decreases of alpha and beta activities and increases of delta and theta activities are associated with brain pathology and general cognitive decline. In the last few decades, many scientific studies were conducted to investigate the effect of inhalation of aroma on human brain functions. The studies have suggested a significant role for olfactory stimulation in the alteration of cognition, mood, and social behavior. This review aims to evaluate the available literature regarding the influence of fragrances on the psychophysiological activities of humans with special reference to EEG changes.

1. Introduction

• The aroma components from natural products have been used for mental, spiritual and physical healing since the beginning of recorded history. In aromatherapy, fragrance substances (aroma/odor/scent) from various natural sources have been used for the treatment of various disorders. The aromatherapy treatment is a natural way of healing a person’s mind, body and soul. Many ancient civilizations, including Egypt, China and India, have used aromatherapy as a popular complementary and alternative therapy for more than thousands of years . In traditional medicine as well as in aromatherapy and herbal medicine, essential oils and fragrance compounds have been used for the treatments of various psychological and physical disorders such as headaches, pain, insomnia, eczema, stress-induced anxiety, depression and digestive problems. In recent years, various studies have revealed that olfactory stimulation through fragrance inhalation exerts various psychophysiological effects on human beings. There are various methods available to administer the fragrances in small quantities, including inhalation, massage or simple applications on the skin surface and, sometimes, they can be taken internally.
• In our daily life, several fragrances appear and a sense of smell plays an important role in the physiological effects of mood, stress, and working capacity. Fragrance is a volatile chemical component with a molecular weight of < 300 Da that humans perceive via the olfactory system. In the olfactory process, the fragrant molecules in the air attach to the cilia of olfactory receptors in the olfactory epithelium, located in the nasal cavity. Then the guanine nucleotide binding protein (G-protein) coupled receptors (GPCR) are activated and electrical signals are generated. Subsequently, the electrical signals are transmitted to the brain by olfactory sensory neurons via olfactory bulb and higher olfactory cortex. Consequently, these electrical signals modulate the brain functions including memory, thoughts, and emotions. Many studies describe that the inhalation of fragrances highly affect the brain function since the fragrance compounds are able to cross the blood-brain barrier and interact with receptors in the central nervous system. Furthermore, many studies have suggested that the olfactory stimulation of fragrances produces immediate changes in physiological parameters such as blood pressure, muscle tension, pupil dilation, skin temperature, pulse rate and brain activity. Hence, the studies in relation to the role of fragrances in the brain functions of healthy and diseased subjects have significantly increased in the past decades.
• There are numerous techniques that have been developed to examine the brain function. The emotional and behavior alterations by fragrance inhalation have been assessed by different electrophysiological methods such as electroencephalograph (EEG), contingent negative variation, near infrared spectroscopy, and functional magnetic resonance imaging. Among them, EEG is the best temporal measure of responses in the central nervous system and is susceptible to alteration during exposure to fragrance. Furthermore, the perfect classification of electrical activity for a particular state of human brain supports the diagnoses of neurological diseases. Previous studies reported that the odors affected spontaneous brain activities and cognitive functions were estimated by EEG. The EEG power spectra were estimated by using Fast Fourier Transform that allows the quantitative analysis of electrical signals in the total as well as in single frequency bands. The EEG spectrum is a complex signal resulting from postsynaptic potentials of cortical pyramidal cells and these signals can be recorded by the metal electrodes placed on the surface of scalp. Based on the above knowledge, we present an overview of scientific experimentation in regards to psychophysiological effects of fragrances with special reference to EEG studies.

2. Fragrance Components

• The fragrances are mainly volatile organic compounds with characteristic, usually pleasant odors. They have been used for thousands of years to deliver a variety of benefits, especially for the physical and psychological well-being of humans. In the 1920s, Rene-Maurice Gattefosse, a French chemist, coined the term aromatherapy, referring specifically to the use of natural fragrance essential oils to treat injury and disease. Nowadays, a variety of consumer products such as candles, perfumes and other personal care products, room fresheners, detergents, etc., are commercially available with aromatherapy benefits. The aromatic properties of these products play a major role in the psychophysiological functions of human beings. The fragrance materials are exposed to consumers ranging from skin contact to inhalation. The fragrance components have some specific molecular properties in order to provide sensory properties. It has a sufficiently high vapor pressure, low polarity, some ability to dissolve in fat and surface activity. Fragrance materials vary from highly complex mixtures to single chemicals. The fragrance molecules are mainly limited to the molecular weight of 200 to 300 Da but within that range, there are essentially a vast number of fragrant components and their molecular structures are highly varied. The natural fragrance materials are mainly obtained from plants, resins, animal secretion and their metabolites .
• Among the various natural fragrant components, essential oils are the main therapeutic agents, which are said to be a highly concentrated volatile and complex mixture of aromatic components obtained from different organs of the plant. There are about 17,500 aromatic plant species from different angiospermic families producing essential oils, particularly Lamiaceae, Rutaceae, Myrtaceae, Zingiberaceae and Asteraceae. The essential oils contain approximately 20–60 different components at various concentrations. They are characterized by two or three major components at relatively higher levels (20%-70%) with several other minor components (trace amounts). In general, these major components are responsible for the biological potentials of the essential oils. The components of essential oils are classified into two major groups (terpenes and aromatic compounds) based on their biosynthetic origin. The terpenes are the largest group of natural fragrances. The classification of terpenes is mainly based on the number of isoprene units present in their structure. Depending on the number of C 5 units, the terpenes are classified into hemiterpenes (C 5), monoterpenes (C 10), sesquiterpenes (C 15) and diterpenes (C 20). Based on the functional groups, the terpenes and other aromatic compounds have been classified into hydrocarbons, alcohols, aldehydes, ketones, phenols, esters, ethers, etc.. Thousands of different terpene and aromatic structures occur in perfume ingredients, both natural and synthetic.
• In the terpenes, monoterpenes are the most abundant molecules of the essential oils (about 90%) with a great variety of structures. Geraniol/nerol, linalool, citronellol, citronellal and citral are the most important terpenes and are widely used in the perfume industries. In aromatherapy, the medicinal and aromatic plants including bergamot, caraway, eucalyptus, geranium, juniper, lavender, lemon, lemongrass, mint, orange, peppermint, pine, rosemary, sage, tea tree, thyme and ylang-ylang have been used to cure a variety of physical and psychological disorders. These plants contain various bioactive monoterpene and sesquiterpene components along with other aromatic components. shows the names of some important essential oil-bearing plants with their major bioactive components. Some of the fragrance components from animal origin such as macrocyclic ketones and esters as well as aromatic nitro compounds and polycyclic aromatics (group of musk fragrances) are also widely used in the perfume industries. The natural fragrances from plants and animals were predominantly used until the end of the 19th century. At present, synthetic fragrances are increasingly applied due to the constant and reproducible quality over natural fragrances.

3. The Olfactory Process

• Olfaction is a prehistoric sense for humans and animals. It permits vertebrates and other organisms with an olfactory system to identify food, mates, predators, and provides both sensual pleasure as well as warnings of danger, such as spoiled food or chemical hazards. In humans and animals, it is one of the important means by which our environment communicates with us. Previous studies stated that even a small amount of fragrance compounds taken by respiration causes indirect physical effect by activating olfactory memory. In addition, the fragrance and the sense of smell are very important in the direction of human behavior.
• The olfactory system contains a sensory organ (olfactory epithelium) and specific olfactory brain regions (olfactory bulb and higher olfactory cortex). The olfactory mucosa is the region which is located in the superior and posterior part of the nasal cavity, especially for the detection of fragrant molecules. It includes the olfactory epithelium and its underlying lamina propria. In general, the olfactory epithelium undergoes a continual process of neurogenesis in which new neurons are constantly generated throughout adult life, and this is the reason for discontinuity and spread of the olfactory mucosa. The olfactory receptor cells contain cilia where molecular reception with the fragrance occurs and sensory transduction starts. At one side, the olfactory receptor neurons extend through the epithelium to contact fragrant molecules in the air. At the other end, the olfactory receptor cells in the epithelium form axons to penetrate the cribriform plate of bone, reaching the olfactory bulb of the brain where they converge to terminate with post-synaptic cells to form synaptic structures called glomeruli. Each glomerulus receives input from olfactory sensory neurons expressing the same type of odorant receptor. The glomeruli are connected in groups that converge into mitral cells and tufted cells. The mitral cells and tufted cells are the primary efferent projection neurons of the olfactory bulb. From the mitral cells, the olfactory information is transmitted directly to the higher olfactory cortex in the corticomedial amygdala portion of the brain through olfactory tract where the signaling process is decoded and olfactory interpretation and response occurs.

• The olfactory process begins when fragrances from the atmosphere enter into the nose and attach to the cilia of receptor cells. In general, fragrance stimulation of olfactory receptor cells in the nose involves interaction of fragrance molecules with olfactory-receptor proteins. Researchers found the family of transmembrane proteins believed to be the odor receptors and some of the genes that encode them. They found that the proteins contained the seven-helical transmembrane structure and contained sequence resemblance to other members of the G-protein-coupled receptor family. The previous studies reported that humans have about 350 active odorant receptor genes and about 560 odorant receptor pseudogenes. The olfactory events undergo two different G-protein-coupled transduction mechanisms; one activating adenylyl cyclase to generate cyclic adenosine monophosphate, the other activating phospholipase C to produce inositol trisphosphate. Then they open channels admitting calcium, sodium and chlorine ions into the cell, leading to depolarization of the membrane and an action potential. Then the olfactory sensory neurons send the electrical signals to the brain via olfactory bulb and higher olfactory cortex. The discovery of the olfactory receptor genes provides new genetic and molecular techniques for pursuing the organization of the olfactory pathway in the brain.
• The olfactory system is described by relatively direct connections to brain structures involved in memory and emotion such as the hippocampus, thalamus, and frontal cortex. The olfactory tract carries the axons leaving the olfactory bulb and projects to the structures collectively called the primary olfactory cortex. The piriform cortex is the largest of the olfactory areas and occupies a central position in the primary olfactory cortex. The piriform cortex in humans appears to be involved in odor recognition memory. The other important cortical primary olfactory areas include the anterior cortical nucleus of the amygdala, the periamygdaloid cortex, and the entorhinal cortex. Olfactory information is transmitted from the primary olfactory cortex to other cortical and subcortical areas. Further, the periamygdaloid and the entorhinal cortex provide olfactory information to the amygdala and hippocampus.

4. Electroencephalography (EEG)

• The EEG power spectra were determined by Fast Fourier Transform that allows the quantitative analysis of signals in the total as well as in single frequency bands. The neuronal activity in the brain was detected by recording the EEG signals from the scalp or the surface of the brain. The EEG signals arises from excitatory (depolarizing) and inhibitory (hyperpolarizing) post-synaptic potentials in populations of pyramidal neurons, which are located in the lower layers of the cerebral cortex. The EEG power spectra bands frequently applied for examining the brain activity are the delta (0–4 Hz), theta (4–8 Hz), alpha (8–13 Hz) beta (13–30 Hz) and gamma (>30 Hz) waves.
• The EEG recording is relatively simple, non-invasive and could serve as an objective method for evaluating the olfactory system. It is possible to achieve results in a short period of time, and it does not require active cooperation of subjects. Small disc-shaped metal electrodes are fixed to different locations on the subject’s scalp according to the International 10–20 system. Further, electrode gel is used to enhance the contact between the scalp and electrodes. The electrode epidermal impedance must be less than 5 kΩ before reliable recordings can be made. The electrodes detect the sum of positive and negative charges in their vicinity [ 36]. The studies of odor-related EEG may lead to understanding the psychophysiological activities induced by various fragrances.

4.1. Brain Waves and Their Functions

• Brain waves naturally appear during both the active and resting states. Our thoughts, emotions and behavior are the reflection of neuronal activity within the brain. The activation of brain waves characterizes the neuronal electrical activity, particularly the voltage fluctuations from ionic flows of neurons in the brain. The EEG measures these electrical activities and represents them as waves or oscillations. Commonly, these brain waves are representative of specific functions throughout the brain. The EEG may be affected by sleep, brain disorders, medication and age . There are many separate wave bands ranging from 0.05 to 500 Hz that have been operationally expressed based on different states of the brain function. The brain waves with slower frequencies are dominant when we feel tired, slow, or dreamy. On the other hand, the higher frequencies are dominant when we feel wired or hyper-alert . The following categories of frequency bands are the most therapeutically relevant.

4.1.1. Delta Waves

• Delta waves (0–4 Hz) are the slowest and the most important EEG feature of human non-rapid eye movement sleep (dreamless sleep), which have their origin in cortical layers. This kind of sleep is also called slow wave sleep because the EEG activity producing slow waves with a frequency of <1 Hz. They are normal in sleeping adults and children, but abnormal in awakening adults. These waves are the most common focal pathological waveform .

4.1.2. Theta Waves

• Theta waves occur between the frequencies of 4–8 Hz during sleep and are also dominant in deep meditation. These waves are transiently found in 15% of the normal population and occur in both cortical and hippocampal regions. When compared to adults, children tend to have a significantly higher level of theta activity. The theta state is also connected with subconscious fears, worries and nightmares. Further, these waves indicate sleep, drowsiness, daydreaming, as well as creative and imaginative thinking that is controlled by the subconscious mind. The theta waves play a major role in the function of short-term memory and the process of building memories.

4.1.3. Alpha Waves

• Alpha waves have frequencies from 8 to 13 Hz. They occur in all age groups with closed eyes but are prominent in adults. In particular, alpha waves occur while an individual is temporarily idle, but still alert. These waves occur during moderate levels of brain activity and are found in the cortex, occipital lobe, and thalamic regions. In addition, the alpha waves play an important role in networking between neurons. It was reported that the alpha frequency is highly associated with cognitive performance. In particular, the increases in alpha wave activity have also been correlated with an enhanced perception of calmness. Overall the alpha waves are connected with mental coordination, calmness, alertness, integration and learning states of the brain.

4.1.4. Beta Waves

• The frequency range of beta waves is 13–30 Hz and normally occurs during a heightened state of awareness. They are a fast wave activity and occur when we are alert, attentive and engaged in problem solving, decision making, and focused mental activity. The beta waves are further divided into three bands such as low beta, mid beta and high beta. The beta waves occur once a task is being completed, and throughout active concentration. The activation of beta waves is mainly associated with benefits in academic performance and these waves significantly increase one’s cognitive skills. Further, the beta waves have also been reported to affect mental conditions. In general, beta wave activity decreases during the drowsiness state and increases during highly alert.

4.1.5. Gamma Waves

• Gamma waves usually occur at the frequency of >30 Hz and these brain waves are mainly involved in conscious attention with establishing neuronal circuitry. These are the fastest brain waves and correlate with simultaneous processing of information from different brain areas. They are usually found during working-memory matching and expanded consciousness, spiritual emergence and also during hypnotic states.

4.2. Brain Lobes (Regions) and Their Functions

• The brain regions are categorized into frontal, temporal, parietal and occipital regions and each region has specific functions. However, many activities require coordination of multiple areas in both hemispheres.

4.2.1.

• The frontal region is located just beneath our forehead and it consists of all cortical areas anterior to the central sulcus. This region consists of a number of different functional areas such as the primary motor area, the premotor area and the prefrontal cortex. The prefrontal region is the most important functional zone of frontal region. It regulates the physiological constructions of memory, perception and intricate action, and diverse cognitive processes. This region mediates a variety of higher cortical functions essential for planning, language, social interactions, and having a general executive oversight of other brain regions. Collectively, the frontal region is associated with a number of components including reasoning, planning, problem solving, parts of speech, intellect, behavior, attention, movements, sense of smell and personality.

4.2.2. Parietal Region

• The parietal region is situated between the frontal and occipital regions. This region contains the postcentral gyrus, superior parietal lobe, parietal operculum, supramarginal gyrus, and angular gyrus. This region is also divided into two functional areas: an anterior zone (somatosensory cortex) and a posterior zone (posterior parietal cortex). The parietal region plays important roles in integrating the sensory information from various parts of our body, understanding spatial orientation, recognition and perception of stimuli. The somatosensory cortex is essential for processing touch sensations and, especially helps to discriminate between sensations such as temperature and pain.

4.2.3. Temporal Region

• The temporal region is located near the ears and is mainly associated with auditory information, memory, emotion, conceptual understanding and in the perception of spoken and written language. It was reported that the right hemisphere of this region is related to creative processing, and the left hemisphere is related to logical processing.

4.2.4. Occipital Region

• The occipital region is the most posterior portion of the human cerebral cortex. This region is mainly associated with visual information processing (reception, orientation, motion, and color recognition) and communication with the cerebral cortex. The surface area of the human occipital region is about 12% of the total area of the neocortex of the brain.

4.3. Administration of Fragrances

• The EEG measurement room is maintained at a constant room temperature and humidity. The administration methods of fragrances to study the EEG activity were varied among the authors. In general, the fragrance administration has been carried out by a known volume of fragrance (diluted or undiluted), was dropped on the filter paper or perfume’s test strip and then placed about 3–10 cm in front of the subject’s nose. Fragrances were also presented to the subject by a funnel-shaped supplier fixed on the chest (15 cm under the nose) with a flow rate of 2000 mL oil/min . In another study, three drops of essential oil were added on a sterile dental swab and placed in a pierced metal container (6 cm wide × 6 cm long) and placed about 15 cm above the infant’s head and out of view from the infant. Researchers administered the fragrances to the subjects by using the sample chamber placed 5 cm in front of the nose. Briefly, 0.05 g of fragrances were spotted on the filter paper and placed inside an 80 mL sample chamber, and then odorless air was pumped into the chamber (flow rate at 1 L/min).
• Recently, some researchers followed the odorant delivery system using a constant flow-olfactometer (flow rate at 1.0 L/min). Air from the chamber was transmitted through additional stainless tubing to a modified mask immobilized at 15 cm from the nose of a subject. A particular amount of fragrance oil was administered using an oxygen pump system through a plastic tube via respiratory masks (flow rate at 2 L/min). In another report, a known volume of diluted fragrance oil was added in a plastic bag and administered through a mask. In a recent study, a nebulizer was used for the administration of fragrance oil. The subjects were instructed to inhale the fragrance from the nebulizer nodule with a distance of approximately 10 cm between their nose and the nebulizer nodule.

4.4. EEG Measurement

• For the EEG study, the International 10–20 system for electrode placement defines 21 standard scalp coordinates derived from four anatomical landmarks such as nasion, inion, and two preauricular points. The electrode placement regions are prefrontal or frontopolar (Fp), frontal (F), central ©, temporal (T), parietal (P), occipital (O) and auricular (A). In these sites, odd numbers are denoted to the left side, even numbers are denoted to the right side and zero (z) is referred to as the sagittal midline. The electrode placement sites on the scalp are expressed based on 10% or 20% of the distance between the nasion and inion, between the two pre-auricular points . Most of the EEG recordings are based on simplified forms of signal data processing such as the Fast Fourier Transform. During the EEG measurement, the subjects are seated in a comfortable chair and are instructed to sit quietly, close their eyes and to breathe normally. The silver/silver chloride or gold electrodes are mainly used for the EEG study. In addition, the electro-caps made of an elastic spandex-type fabric are frequently used instead of individual electrodes. Depending on the purpose of the study, the EEG readings are recorded from different electrode sites according to the International 10–20 System.

• Researchers used 28 electrodes attached to an elasticated cap placed on the scalp according to the International 10–20 System. The EEG signals were recorded for the frequency bands such as delta, theta, alpha 1, alpha 2, beta 1, beta 2 and beta 3. Total power was determined for the frequency range 0.5–30.0 Hz. Researchers recorded EEG readings from 12 scalp positions using multichannel biological amplifiers with a band-pass filtering between 0.1 and 32 Hz. Researchers employed the EEG recordings obtained from 21 shallow cup Ag electrodes placed on the scalp. The set of 31 electrodes were also used for the EEG study. The electrodes included eight channels (Fp1, Fp2, F3, F4, T3, T4, P3 and P4), and a grounding electrode to the left earlobe, and a standard electrode to the right earlobe were frequently used in the EEG study.
• The EEG recordings with eye blinks or motor artifacts were removed for each channel. All electrodes are referenced to the ipsilateral earlobe electrodes. The recording time for fragrance inhalation study is varied according to the authors (from few seconds to minutes). The standard bandwidth is 0.5–70 Hz with the 50 or 60 Hz notch filter. For standard EEG, the highest frequency is 70 Hz, and 200–256 Hz sampling is sufficient; the readings are stored in a computer by the analog to digital conversion. The electrode gel is applied into each electrode to connect with the surface of the scalp in order to drop the electric resistance of the scalp below 5 kΩ. The mean power values are calculated as microvolts square (mV 2), and the frequency bands such as absolute delta, theta, alpha, beta (low beta, mid beta and high beta) and gamma are recorded. The topographical mapping (t-mapping) of EEG brain waves was constructed by using software packages provided by the respective EEG instrument manufacturers. The t-maps may clearly illustrate differences which are difficult to understand in a table of EEG power spectra values. The statistical software packages are used for data analysis (Analysis of variance (ANOVA)/ t-test) on EEG activity before and during the exposure of fragrances based on the EEG power spectrum values.

5. Effect of Inhalation of Fragrance on EEG Activity

• Several studies have shown that the effects of various fragrances on mood, physiology and behavior are due to the fragrance’s direct and intrinsic ability to interact and affect the central nervous system. In addition, fragrances highly influence the various mental and physical conditions of human. The EEG recording is the simplest and precise technique to understand the effect of fragrances on brain function. In the EEG study, the subject is seated quietly and asked to inhale a fragrance of interest to the investigator. Subsequently, EEG data are gathered during this olfactory stimulation and later analyzed shows the details of previous studies in relation to influences of aroma inhalation on human EEG activity.

Table 2

• Researchers clearly reviewed the human EEG and odor response and discussed the association between olfaction and language. Researchers stated that the measurement of brain electrical activity using EEG recordings is now providing interesting new information on how odor signals are processed by the brain. Further, Researchers reviewed the therapeutic effects of odors on health-related behavior. Researchers suggested that the EEG recordings from more anterior electrodes could be related to psychometric responses. Researchers found that the brains of professional perfume researchers respond to odors mainly in the frontal region, exhibiting the function of the orbitofrontal cortex due to the occupational requirement of these subjects to discriminate or identify odors. In another study, the combined form of Tai Chi/Yogasignificantly increased the relaxation state as well as tended toward an increase of EEG theta activity. Researchers reviewed the scientific studies explaining olfactory effects on mood, physiology and behavior. Researchers clearly described the pharmacological and psychological hypotheses behind the previous reports. Researchers stated that the sensory, motor, and hippocampal cortices interact intimately. Brain creates the contextual richness of relevant knowledge and expresses remembrances in spatial patterns of amplitude modification of beta and gamma waves.
• Aromatic hydrocarbons are the most widely used solvents in the industries that cause central nervous system symptoms in exposed workers. Researchers conducted the effect of low concentration odor of galaxolide on central nervous system activity even when undetected. Significant differences were observed in alpha activity between the undetected odor and no odor control conditions. Further, the authors suggested that odors may be distracting or produce divided attention even when undetected. Researchers reported that during the early phase exposure of m-xylene increased the dominant alpha frequency and alpha percentage. Researchers investigated the effect of phenylethyl alcohol (pleasant) and valeric acid (unpleasant) on EEG activity and suggested that smelling an unpleasant odor leads to a cortical deactivation by increasing alpha 2 power.
• In the EEG study, the activation of alpha wave is the most important parameter and mainly influenced on the positive/negative psychological changes during the exposure of fragrant molecules. Researchers suggested that the increasing trend of alpha wave after gum-chewing exhibited arousal psychosomatic responses. The lavender oil inhalation significantly decreased alpha 1 (8–10 Hz) activity at parietal and posterior temporal regions. Significant changes of alpha 1 were also observed after the inhalation of eugenol or chamomile. These data revealed that the decrease of alpha 1 activity is highly correlated with comfortable state of subjects. Researchers investigated the effect of the aroma of soybeans heated to various temperatures in order to understand the relationship of the amino-carbonyl reaction products upon EEG. These results suggest that the aroma products from amino-carbonyl reaction increase alpha wave activity. Researchers found that the slow alpha (8–10 Hz) and theta activities significantly increased in the occipital region during the exposure to neroli oil and grapefruit oil when compared with activities before exposure and suggested that these oils reduce the cortical deactivation, or promote a relaxed state. In another study, it was reported that the odor of incense may enhance the cortical activities and the function of inhibitory processing of motor response by significantly increasing the fast alpha activity in bilateral posterior regions. In general, the higher alpha wave activity is highly correlated with the reduced level of stress state.
• In regards to theta wave activity, the changes in theta reflect modifications in attention or cognitive load, with a reduction in theta indicating a reduced level of attention. The effect olfactory stimulation of synthetic (chocolate, spearmint, almond, strawberry, vegetable, garlic, onion and cumin) and real food (chocolate, baked beans and rotting pork) odors on human central nervous system activity was investigated. Chocolate and spearmint odors significantly reduced the theta activity when compared with no-odor control. Researchers reported that the odors of birch tar, jasmine, lavender and lemon significantly increased the theta activity. In addition, Researchers investigated the acute sedative effects of eight different plant extracts such as Valeriana officinalis, Lavandula off., Passiflora incarnata, Piper methysticum, Melissa off., Eschscbolzia californica, Hypericum perforatumand Ginkgo biloba. Among the different plant extracts, valerian extract significantly increased delta and theta activities and also decreased beta activity. Researchers studied the task-related EEG changes during the performance of a mental arithmetic task, as influenced by low alcohol dosages and reported that task-related significant theta power increase was observed particularly in the frontal area. Researchers investigated the influence of fragrances with sedative effects (lemon, lavender and sandalwood) and awakening effects (jasmine, ylang-ylang, rose and peppermint) on visual display terminal task (VDT) activities. The results revealed that fragrances affected subject’s concentration on work and mentally stabilized them when compared with no fragrance control. Researchers found that the essential oil of the Siberian fir tree, Abies sibirica (Pinaceae) increased theta activity after the VDT. These results showed that the essential oil of A. sibirica significantly reduced arousal levels after the VDT task.
• Researchers investigated brain electric field signatures of subjective feelings after chewing regular gum or gum base without flavor. Pre-post changes of source locations for the alpha 2 band and beta 2 band and of Global Field Power for delta to theta, alpha 2 and beta 1 decreased due to chewing regular gum and increased due to chewing gum. Subjective feeling changed to more positive values after regular gum when compared with gum base. Further, the author suggested that the chewing gum with and without taste or smell activates different brain neuronal populations. Further, Researchers evaluated the effect of a chewing gum with and without flavor on the EEG activity. Chewing the standard gum base increased the alpha wave and decreased the beta wave. On the other hand, alpha and beta wave activities significantly increased when chewing the flavored standard gum as well as inhaling the flavored aromatic oil. In addition, significant change in the ratio of theta wave in the frontal area was observed when chewing the flavored standard gum. The results suggested that the flavor as well as chewing could enhance the concentration with a harmonious high arousal state of the brain function.
• The isomers of aromatic compounds possess different fragrance qualities and intensities for humans. For example, in the case of enantiomers of 3-methylthiobutanal, one has a specific aroma and another one is odorless. Because of fragrance variations among the isomeric aroma components, their medicinal and biological properties also significantly varied. The sedative properties of linalool were investigated using the optically active linalools (( R)-(−)-, ( S)-(+)- and ( RS)-(±)-forms). After hearing environmental sound, ( RS)-(±)-linalool significantly decreased beta wave activity after work when compared with the before work and the same activity was also observed for ( R)-(−)-linalool. However, the feature was just the reverse in the case of ( S)-(+)-linalool [ 88]. In another study, researchers investigated the effects of inhalation of optically active linalools on humans in order to determine their odor distinctiveness by chiral isomers (( R)-(−)-linalools and ( S)-(+)-linalools). From the results, the authors concluded that enantiomeric stereospecificity of linalool induced different odor perception and responses with chiral and task dependence. Researchers studied the olfactory stimulation of isomeric aroma components, (+)-limonene and terpinolene on EEG activity. According to gender variation, women responded well to both the compounds by a significant increase of absolute fast alpha activity. Further, the isomers exhibit diverse states of brain function as they affect different sites of the brain.
• The EEG recordings were also used to investigate the influence of listening to soft music with/without inhaling Citrus bergamia aroma on the autonomic nervous system activity. The negative change of the ratio of low frequency to high frequency was observed in the music group, the aroma group, and the combined groups but not the control group. Listening to soft music and inhaling C. bergamia essential oil increased the relaxation state of brain. Researchers used the EEG recordings to investigate differences in hemispheric activation associated with different hedonic responses to a low concentration of a single compound (damascenone: fruity, berry smell). In their study, the results revealed that a non-significant trend for left frontal differences in EEG were due to different liking responses to damascenone, and these changes suggested quantification of the neurophysiological effects associated with odor liking. Researchers found that the beta wave activity increased in the left frontal brain region due to a pleasant odor. Researchers examined the relationship between odor responses of consumers to different flavor components ( para-cresol 4-methylphenol, 2-heptanone, methional, 3-methylthiopropionaldehyde and dimethyltrisulphide). Researchers suggested an ability of sensory ratings and brain recording techniques to reveal differences in responses associated with variations in background and experience.
• In the psychophysiological properties of aroma, lavender is the most studied plant. The four important Lavandula species are L. angustifolia, L. stoechas, L. latifolia, and L. intermedia. The different lavenders have same ethnobotanical properties and major chemical constituents (geraniol, linalool, linalyl acetate, β-caryophyllene, β-ocimene, terpinen-4-ol and camphor). Lavender is mainly employed in aromatherapy treatments including inhalation, aromatherapy massage, dripping oil and bathing. Previous studies suggest that lavender has anxiolytic, mood stabilizer, sedative, analgesic and other neuroprotective properties . Researchers assessed the influence of lavender and rosemary on EEG activity, alertness, and mood. The authors suggested that the lavender group increased drowsiness by increasing beta power and the rosemary group increased alertness by decreasing frontal alpha and beta power. Further, lavender and rosemary fragrance may induce left frontal EEG shifting in adults and infants who show greater baselines relative to EEG activation in the right frontal region. Researchers investigated the effect of exposure of lavender or rosemary on EEG activity (based on EEG asymmetry) and suggested that infants of depressed and non-depressed mothers respond differently to odors. In addition, the effect of L. angustifolia aroma on the brain electrical activity in female adults with sleep disorders was investigated. Results showed that L. angustifolia aroma decreased alpha activity in the occipital and parietal regions, and increased the theta and beta activities in the frontal and occipital regions, respectively, in subjects with good sleep quality. On the other hand, L. angustifoliaaroma increased the theta activity in the all cranial regions in subjects with poor sleep quality. These data suggested that L. angustifolia aroma may have beneficial effect for female adults with sleep disorders.
• Further, the inhalation of lavender oil resulted in more active, fresher, and relaxed subjects than those inhaling base oil. Lavender oil increased the theta and alpha wave activities when compared with base oil. The topographic map showed obviously more scattering power particularly in bilateral temporal and central area for alpha waves. These changes suggested the relaxing effect of inhaling lavender oil. Recently, the effect of lavender ( L. angustifolia) and bergamot ( Citrus bergamia) essential oil inhalation on EEG recordings was studied. The inhalation of essential oils significantly increased the absolute theta in the right prefrontal region. There were also significant differences in the relative fast and slow alpha after the inhalation of essential oil when compared with the control group. These EEG changes revealed that both the physical and mental states became more stable and relaxed after the inhalation of essential oil. Further, a mixture of lavender and bergamot oil was more effective than lavender oil alone. These reports clearly suggest that lavender oil may be an effective medicine in the treatment of various psychophysiological disorders.
• In other studies, the essential oil from the seeds of Zizyphus jujubasignificantly decreased the theta wave and increased the relative fast alpha, relative gamma, and spectral edge frequency 50%. Especially the relative fast alpha wave increased significantly in the left, right prefrontal, and left frontal regions during the inhalation of Z. jujubaessential oil. These changes suggested that the Z. jujuba seed oil increases the attention and relaxation states of brain. In another study, researchers determined the effect of fragrant chemicals of essential oil from the aerial parts of Mentha arvensis L. f. piperascens on EEG activity. The relatively fast alpha activity significantly increased during the inhalation of M. arvensis. On the other hand, the values of gamma and the spectral edge frequency 90% were significantly decreased. Researchers suggested that these EEG changes were associated with the reduction of mental stress. Further, researchers evaluated the effect of supercritical carbon dioxide extract of Magnolia kobus flower buds on EEG changes. During the inhalation of M. kobus fragrance, a significant decrease of absolute alpha wave was observed in the left parietal region. The results reveal alterations in EEG activity to awaken and enhance the concentration states of brain. Researchers reported that the inhalation of jasmine oil increased the beta wave activity in the anterior center as well as the left posterior regions. These changes were associated with the increase of positive emotions such as the feeling of well-being, or feeling active, fresh and romantic. Researchers found that impaired higher-order olfactory processing in temporal lobe epilepsy patients may inhibit the effects of the ylang-ylang aroma on the P300. Researchers investigated the memory task performance and the central nervous activity after smelling two kinds (Koushun and Kouju) of pan-fired Japanese green tea to examine their physical and psychological effects. The results showed that the odor of Kouju may induce a positive emotion. It may also affect the beta 1 activity at right frontal region and improve memory task performance.
• Researchers examined human central nervous system response to the odors of lemon, peppermint, and vanilla. The theta wave activity showed significant difference due to the inhalation of fragrances and suggested that olfactory stimuli can affect the frequency characteristics of the electrical activity of the brain. Researchers studied the electrophysiological response to food (strawberry) and non-food-related (lily of the valley) odors in healthy volunteers. The results showed specific scalp potential maps for the two conditions. The source of the map in the food condition seemed to be associated with the processing of rewards, whereas the specific map in the non-food condition reflects odor characteristics excluding the reward. Researchers investigated the effect of essential oil inhalation of Inula helenium root on human EEG activity. The absolute theta (all the regions except T3), beta (Fp1) and mid beta (P4) and relative theta (Fp1, Fp2, F3 and F4) wave activities significantly decreased during the essential oil inhalation compared to before inhalation. The changes in EEG activities due to the essential oil inhalation of I. helenium root may increase the alertness state of brain.
• The gender variation also plays an important role in the EEG recordings. Some of the previous studies suggested that the brains of male and female humans are differentially lateralized in relation to cognitive function. In addition, the EEG activity of resting males and females were different in the excitability dynamics of their cortical networks, and also gender differences were found in the stimulus and non-stimulus conditions. Researchers studied the gender differences in the EEG during cognitive activity during rest and during solution of three series of tasks — analytic, spatial and mixed — demanding both kinds of processing. The results revealed that men showed significantly higher relative beta activity when compared to women, while women showed significantly higher relative alpha activity than men. Further, the gender variations are noticeable in event-related oscillations during simple visual stimulation. Recently, researchers reported that absolute and relative beta activities changed significantly more in men than women during the inhalation of isomeric components, (+)-limonene and terpinolene. In addition, the absolute fast alpha activity increased significantly more in women than men during the inhalation of these isomers. The previous reports clearly revealed that the variation in the EEG studies can be attributed to differences in EEG recording techniques and conditions, gender, as well as in the type and quality of fragrances administered.

6. Effect of Inhalation of Fragrance on Psychophysiological Activity

• The positive effect of fragrances is mainly related to human behavior. The findings of the previously reported studies suggest that the olfactory system plays a major role in central nervous system functions. Studies reviewed the physiological effect of olfactory stimuli in humans. Studies also reviewed the evidence for the effectiveness of aromatherapy in the treatment of high blood pressure. Studies investigated the interactions between texture and olfactory sensations, using a psychophysical and an electrophysiological approach. A butter aroma was presented either orthonasally or retronasally after oral processing and before swallowing the oral stimulus or in the absence of an oral stimulus. Studies suggested that the perceptual interactions occurred between food texture and odor, with cross-modal interactions being found for both orthonasal and retronasal odor administration. Further, these interactions between texture and odor occur at both primary-sensory and cognitive evaluative levels of stimulus processing. Research investigated the effect of food words such as odor, taste, vision or somatosensory texture and reported that the semantic dimensions influence neuronal processing of words in relation to multisensory perception. Studies clearly described the relationship between mood change, odor and its physiological effects in relation to verbal and non-verbal changes in humans induced by inhaling essential oils and individual components (linalool and its enantiomers).

Table 3

• Researchers studied the anxiolytic effects of inhalation of geranium and rosemary & reported the perceptional change of fragrance of essential oils such as ylang-ylang, orange, geranium, cypress, bergamot, spearmint and juniper in relation to type of work (mental work, physical work and hearing environmental sounds). The data confirmed that essential oil inhalation affected a different subjective sensitivity of fragrance depending on the type of work. In their study, inhalation of cypress after physical work produced a much more favorable impression than before work. For mental work, inhalation of juniper appeared to create a favorable impression after work. Studies stated that orange odor reduced anxiety and increased positive mood and calmness in women. Another study investigated the effects of inhaling aromas (rose, jasmine and lavender) of preference on physical exercise in college students. The results revealed that the inhalation of preferred aromas suppressed the muscle sympathetic vasoconstrictor activity. In regards to sympathetic activity of aroma, essential oils from pepper, estragon, fennel or grapefruit increased relative sympathetic activity when compared with an odorless solvent (triethyl citrate). On the other hand, essential oils of rose or patchouli decreased relative sympathetic activity by 40% . In addition to essential oil aromas, the individual odor components also affect the autonomic nervous system responses. In general, human behaviors are closely linked to attention processes, which range from sleep to wakefulness. The aroma of essential oils such as peppermint, jasmine, ylang-ylang and individual essential oil components (1,8-cineole and menthol) significantly influenced basic forms of attention behavior . Researchers studied the influence of enantiomers of limonene and carvone (chiral fragrances) on the human autonomic nervous system and on self-evaluation. They found that prolonged inhalation of fragrances affects autonomic nervous system parameters and states of brain. Further, the chirality of odor components appears to be a major factor in relation to the biological activity of fragrances.
• Researchers reviewed the effect of lavender oils on psychophysiological properties. The essential oils obtained from various species of Lavandulahave been used in cosmetics and pharmaceutical industries for centuries. Among the various species, the L. angustifolia, L. latifolia, L. stoechas and L. x intermedia are the most commonly used plants. Researchers also suggested that lavender aroma significantly reduced the stress and enhanced the arousal states of brain. In patients with severe dementia, an aroma stream with lavender oil shows modest efficacy in the treatment of agitated behavior. Researchers evaluated the olfactory effect of lavender and rosemary essential oils on cognitive performance and mood. In their study, the members of both the control and lavender groups were considerably less alert than the rosemary condition. It was reported that rosemary and lavender scents were associated with lower mean ratings on the fatigue-inertia subscale .
• Researchers studied the effects of lavender (relaxing odor) and neroli (stimulating odor) on mood. Relaxing odor decreased heart rate and skin conductance, whereas stimulating odor produced the reverse effects under equivalent conditions. Studies reported that lavender reduced the pain intensity and pain unpleasantness after treatment. Further, lavender serves as a mild sedative and is used for enhancing deep sleep in young men and women . Influence of orange and lavender essential oils on anxiety, mood, alertness and calmness in dental patients was investigated. The results revealed that, compared to control conditions, both odors of orange and lavender reduced anxiety and improved mood in patients waiting for dental treatment. In another study, the impact of lavender-scented bath oil on mothers and their infants was reported. During the bath with lavender-scented oil, the mothers touched their infants for a longer amount of time, were more relaxed and smiled more. In addition, their infants cried less and spent more time in deep sleep after the bath. These behavioral data suggest that lavender increased relaxation state of the mothers and their infants. Researchers reported that lavender significantly decreased stress levels and the bispectral index values as well as the pain intensity of needle insertion. Researchers investigated whether exposure to aromas (jasmine and lavender) during recess periods affects work performance. In their study, lavender significantly increased concentration levels, but jasmine did not produce such an effect. In addition, researchers reported that aromatherapy (lavender, rosemary, lemon and chamomile) massage produced beneficial effects on anxiety and self-esteem in Korean elderly women.
• In the athletic task performance, the peppermint odor significantly increased running speed, hand grip strength, and number of push-ups, but had no effect on skill-related tasks. Researchers studied the effects of odor (peppermint oil, jasmine oil and dimethyl sulfide) administration on objective and subjective measures of physical performance of athletes. From the results, peppermint odor exhibited more slow-wave sleep and more total sleep and it also produced gender-differentiated responses. In addition, the effect of peppermint oil on exercise performance in young male college students was reported. Researchers found a significant performance improvement in the presence of peppermint odor. Researchers reported that the presence of peppermint oil controlled the increase in sleepiness during 11 min spent in a darkened room when compared with a no-odor condition. Researchers provided the evidence for the impact of the aromas of plant essential oils (ylang-ylang aroma, peppermint aroma) on aspects of cognition and mood. Peppermint significantly enhanced memory and alertness. On the other hand, ylang-ylang lengthened processing speed and increased calmness.
• Researchers studied the effects of transdermal absorption of ylang-ylang oil on physiological parameters and self-evaluation in human. The ylang-ylang oil significantly decreased the blood pressure and increased the skin temperature. Further, subjects in the ylang-ylang oil group rated themselves calmer and more relaxed when compared to subjects in the control group. Researchers examined the effect of the aroma of the essential oil of Roman chamomile ( Chamaemelum nobile) on mood and cognition in human. The authors stated that the subjective alertness was associated with the sedative effect of the aroma and subjective calmness was associated with both the aroma’s sedative effect and stimulated arousal expectancy. Researchers stated that caffeine effectively improved speed and accuracy on cognitive tasks and increased alertness when compared with chewing.
• Researchers investigated the perception of odor (chocolate and lavender) intensity through ortho- and retronasal presentation. The findings of their study suggested that the response was larger when an odor unrelated to food was presented in an unusual site (retronasally) compared with presented in an orthonasal site. The authors stated that the route of odor presentation has direct associations with the enjoyment of foods and drinks. Researchers investigated the influences of heliotropin on nighttime sleep and suggested that this aromatic compound effectively improves sleep. The potential pharmacological relationships between absorbed 1,8-cineole followed by rosemary aroma exposure and mental behavior were studied. The data revealed that different neurochemical pathways were responsible for their action on cognition and subjective state. Researchers reported that the inhalation of eucalyptus oil effectively decreased patient’s pain and blood pressure after total knee replacement surgery.
• Researchers used natural bergamot essential oil extracted from plants and synthesized a chemical essential oil to study their aromatherapy effect in relieving work-related stress. The results showed that the natural bergamot essential oil relieved work-related stress of teachers with various workloads. However, the treatment showed a weak effect on young teachers with a heavy workload. Researchers investigated the electrophysiological response to food- and non-food-related odors in healthy volunteers and the analyses revealed the specific scalp potential maps for the two conditions. Researchers elucidated the psychophysiological effect of inhaling 12 different essential oils and suggested that essential oils may have versatile psychophysiological properties.
• From the literature of previous studies, lavender, peppermint, rosemary, jasmine, ylang-ylang, lemon, geranium, chamomile and spearmint are the most studied aromatic plants. These plants have been used in the aromatherapy for the treatment of various psychological and physiological disorders.

7. Conclusions

• Based on the previous studies, it can be concluded that fragrances directly and/or indirectly affect the psychological and physiological conditions of humans. In addition, the electroencephalograph studies clearly revealed that fragrances significantly modulate the activities of different brain waves and are responsible for various states of the brain. Further, a number of studies have scientifically supported the beneficial use of various aromatic plants in aromatherapy. However, this study in relation to fragrance stimulation on EEG activity has some limitations. The concentration of the fragrances also plays a major role in EEG activity, because a higher concentration provides a higher fragrance density. Hence, results may differ when using different concentrations of the fragrance. Moreover, the EEG recording time is a very important factor in attaining constant EEG readings from various laboratories. Therefore, it is still unknown whether the fragrances will show the same effect for a longer duration of EEG recordings with different concentrations and more participants. In light of these limitations, standardizing and developing a common standard operating procedure for the effect of fragrances on EEG activity (such as recording time, administration method, concentration of fragrance, number of electrode sites and placebo) is necessary. Only then will we be able to understand the exact action of fragrances on human brain function in relation to EEG brain wave changes.
• Though taking care of your health is certainly a year-round task, your immune system is extra vulnerable during the winter months.