Olfaction & Essential Oils
Posted on Aug 31st 2015
For the past 19 years I have been formulating essential oil blends diluted in carrier oil and applying them topically on the skin. I have also combine two or more pure essential oils whose combine synergistic effect can be inhaled to coat the mucous membrane of the upper and lower respiratory system to help fight off primary and secondary infections. The idea of using essential oils for psychological reasons had not been an area I was knowledgeable in however, after taking a course on the aroma of the mind, I began to understand how the olfactory system worked. I made a few case study blends and received very positive feedback on the pleasant scent and the quick effect felt on clients’ state of mind. It was after repeated affirmative results that I realized how effective the inhalation of essential oils could be in helping calm ones’ sympathetic nervous system during a stressful situation.
Jane Buckle states, ”Inhaling essential oils is the fastest method of getting essential oils into the body” (Buckle 2015).In fact, olfaction is the only sense that has a direct route to the brain and the only portion of the Central Nervous System (Brain & Spinal Cord) exposed to the outside world. It is thought that only one aromatic molecule can create a psychological effect on the mind. Intrigued by this notion I decided to learn more about how the sense of olfaction worked, and why.
What I quickly discovered was, when aromatic molecules are inhaled through the nose, some are absorbed into the mucous membrane, and some pass by and stimulate the olfactory epithelium. The olfactory epithelium is a special mucous membrane located at the roof of the inner nasal cavity that contains olfactory nerves. These neurons project dendrite olfactory cilia, tiny microscopic hairs, down through the nasal epithelium and pick up scent molecules.What is interesting is that each side of the nose has a different perception of smell so it is recommended to waft a blend back and forth under each nostril in order to get the full effect. It is thought that this 0.8 square inch area contains approximately 10 million neurons, with at least 20 million cilia clusters surrounded by supporting cells. These cilia clusters are capable of identifying up to 4000 different chemical molecules or odorants. When a molecule stimulates the receptor an electrical message is sent to theolfactory bulb located above the olfactory epithelium. This signal then travels along the olfactory tract to the limbic system and cerebral cortex.
The limbic systemisthe oldest part of the human brain and is considered our sense of survival. It is a rather complex group of brain structure and includes the olfactory bulb, amygdala, and hippocampus. These structures help with odor identification, social and reproductive behavior, emotion and memory and our instinct, drive and automatic response to a stimulus (Arisi 2012). When an aroma is smelled and identified, a message is instantly sent to the limbic system. This action cannot be blocked by the conscious mind. The hippocampus, amygdala and prefrontal cortex are thought to interact with each other and to work synergistically in ones’ emotional response to information and the memories that are formed (Richter-Levin, Akirav, 2000). The amygdala’s roll is to stimulate the release of hormones that help activate or calm down the sympathetic nervous system that controls our fight or flight response. Recent studies are finding an increased size in the amygdala due to the constant stress and lack of down time for the body to reset the natural rhyme of the nervous system. Research is now available to show just how essential oils used for aromatherapy can be a valued complimentary therapy in helping individuals struggling with mental disorders. And did I mention it takes only one molecule to create a reaction in the brain? Thanks to recent research, certain aromatic molecules such as limonene, linalol and linalol acetate have been shown to have an amazing effect on ones state of mind.
Limonene, a Monoterpene found in many citrus oils, has a great deal of importance when it comes to dealing with anxiety. Many individuals suffering from anxiety are thought to have an overactive stress-response due to their amygdala never shuting off the alarm signal to the Thalamus. In other words, these individuals are in constant “Fight or Flight” mode. When an individual is triggered, their response is out of their control. Research is now showing the inhalation of essential oils high in limonene can have an anxiolytic, sedative and harmonizing effect on the nervous system.
One oil showing promising results is Citrus sinensis (Sweet Orange). Through chemical analysis, the amount of d-limone can be as high 95%. Sweet orange has been shown to have an anxiolytic or inhibiting effect on anxiety, a hamonizing effect on the autonomic nervous system, and shown to lower the amount of cortisol in the blood. Sweet orange would be a great choice when working with young children. A 1% dilution in a lotion base could be a wonderful bedtime blend to help calm night time anxiety and reduce sleep issues. It is a happy and uplifting scent that could soon become your childs favorite part of bedtime. I recall reading that inhaling sweet orange was like breathing in the sun. It brightens the spirit and helps one feel joyful. I’ve never forgotten that and to this day and include this oil into as many blends as I can.
Another great essential oil high in limonene is Citrus limon (Lemon). Through chemical analysis the amount of d-limone can be as high as 69.9%. In a recent study, the inhalation of limon exhibited a sedative, anxiolytic and antidepressant effect on mice.(L M Lopes C, 2011). A great way to use lemon would be in a household cleaner. Inhaling the aromatic airborne molecules of your cleansing product could create a calming yet stimulating effect on your mind and increase concentration. It may even make cleaning a joyful experience. Lemon oil can also be used to help improve ones mental focus. In 1988, lemon essential oil was diffused in the work area and found to reduce the amount of typing errors by 54% (Tisserand 1988).
Citrus bergamia (Bergamot) has the least amount of limonene (26 – 42%) but I find it the most appeasing to my sence of smell and the quickest one to have and effect on my mind. Bergamot has been shown to have an anxiolytic, antidepressant, and relaxing effect on the nervous system and is considered uplifting and energizing to the emotional system. Patricia Davis states, "In helping with mental and psychological states, Bergamot is almost the most valuable oil… it is often described as uplifting and I cannot improve on this description” (Davis 1988). I often combine bergamot with lavender and sweet orange and diffuse the synergy during the winter months to help me through the long cold and often cloudy days. This combination helps calm my frustration and desire for sunlight while uplifting my state of mind. Bergamot essential oil is not only made up of (26 – 42%) of d-limone, but also (14.5 – 31.76%) linalol.This means this oil is comprised of up to 75%stress reduction properties. Bergamot essential oil expressed from the fruit peel is considered phototoxic. Robbert Tisserand recommends a maximum dermal amount of (0.4%) or two drops in a 1 oz blend used on the skin. Avoid sunlight or tanning beds for 12 hours if a blend exceeds the two drop minimum (Tisserand 1988).
Linalol, a component of the Monoterpenols chemical family, is a molecule showing great benefits for the mind when inhaled. General therapeutic effects show antidepressant, anxiolytic, relaxant and a sedative effect on the central nervous system. Oils high in linalol such as bergamot, ylang ylang, and lavender all showed very positive results in blends I have created over the years.
Cananga odorata (Ylang Ylang) is one of the most sweetly scented oil I use. The odor is very intoxicating and if smelled too often or used at a high percentage in a blend could cause headache and/or nausea. This oil is best used in a synergy with other like oils to help lessen the strong odor. Ylang ylang’s linalol (23%) content gives this essential oil anxiolytic and relaxing effects on those dealing with depression and stress. One study classified ylang ylang as having a harmonizing effect due to its ability to lower blood pressure and pulse rate as well as increasing attentiveness and alertness. (Hongratanaworakit 2004). My favorite way to use this oil is at night in the bath. Adding only one drop to the running water sweetens the air and blankets my body while in the tub. I can just feel my stress and exhaustion melt away as soon as I enter the bathroom. Ylang ylang’s sedative nature also aids one with sleep issues.Use caution with those who have inflamed skin or dermatitis. Ylang ylang is a possible skin irritant and sensitizer.
I have often used Lavandula angustifolia (Lavender) as a first choice when working with an individual suffering from anxiety or sleep issues. One study found that the synergistic effects of linalol (36%) and the ester, Linalyl acetate, both present in lavender essential oil created an anxiolytic effect when inhaled (Takahashi, 2011). Lavender is considered safe for children and the elderly making this a wonderful blend to help induce sleep or to relax unwanted anxiety.
The last chemical constituent, linalyl acetate is from the ester chemical family. Esters therapeutic action has a relaxing and balancing effect on the central nervous system. Linalyl acetate adds an anxiolytic component when inhaled. Again, bergamot, lavender and ylang ylang all contain linalyl acetate and are great choices when working to lower the stress response. One study found that linalyl acetate works synergistically with linalool and that the presence of both is essential for the whole oil, lavender and ylang ylang, to work as an inhaled anti-anxiety agent (Shutes, 2014).
One thing to always remember when working with essential oils high in limonene and linalol is they are very volatile oils that oxidize quickly. Essential oils may become skin irritants when oxidized and past their shelf life. Citrus oils should always be stored in the refrigerator and used within one to two years. It is best to purchase organic or chemical-free citrus oils to avoid pesticide residue that may be present in the pressed oil.
My perception of how essential oils can affect the mind at
the start of the Aromas of the Mind course and now has change dramatically. Studying the material and my further research
has shown the many benefits associated with linalyl acetate, linalool, and limonene and has taught me the therapeutic benefits these
essential oils have on a person living a stressful life. No complex blend is needed. Thanks to our olfactory system, all one
needs to do is simply waft an open bottle of sweet orange under their nose to
help bring about a sense of relaxiation and peace. I’m looking forward to growing my knowledge in this area so
that I can continue to help individuals cope with stress, anxiety and
Arisi G, Foresti M, Mukherjee S, Shapiro L. 2012.The roles of olfactory stimulus in adult mammalian neurogenesis.Behav Brain Res. 227(2):356-62.
Buckle J. Clinical aromatherapy Essential Oils in Healthcare. Churchill Livingstone, St. Louis, (2015)
Davis, P. Aromatherapy an A-Z.The C.W. Daniel Company Limited, United Kingdom, (1988)
Hongratanaworakit T, buchbauer G. (2004) Evaluation of the harmonizing effect of ylang-ylang oil on humans after inhalation.Planta med. 70(7):632-6.
L M Lopes C, Goncalves e S C, de Almeida AA, da Costa JP, Marques TH, Feitosa CM, Saldanha GB, de Freitas RM.(2011) Sedative, anxiolytic and antidepressant activities of Citrus limon (Burn) essential oil in mice.Pharmazie.66(8):623-7.
Richter-LevinG, AkiravI. Amygdala-hippocampus dynamic interaction in relation to memory. Mol Neurobiol. 2000 Aug-Dec;22(1-3):11-20
Shutes, J. Aromatic Components and Essential Oils.East-West School for Heral and Aromatic Studies, NC, (2014)
Takahashi M, Satou T, Ohashi M, Hayashi S, Sadamoto K, Koiki K. (2011) Interspecies comparison of chemical composition and anxiolytic-like effects of lavender oils upon inhalation.Nat Prod Commun.6(11):1769-74.
Tisserand, R., Lemon Fragrance Increases Office Efficiency. IJA. VOL. 1, NO. 2, (1988), P.2.
Watts, G.O., Dynamic Neuroscience:Its Application to Brain Disorders.Harpers and Row, New York, (1975)