Olfactory receptors are protein molecules that detect odours in the environment.
In recent years there have been several studies confirming that olfactory receptors are found in different parts of the body other than the nasal epithelium. A review published in 2018, Human Olfactory Receptors: Novel Cellular Functions Outside of the Nose (Maßberg D & Hatt et al.) confirmed: "that different systems in our body including the integumentary system (skin and appendages) can identify terpenoids and act as cues for physiological reactions." Making essential oils a target to further study the activation of olfactory receptors throughout the body.
Some aromatic components investigated are citronellal, citronellol, eugenol and beta-Ionone (Maßberg D & Hatt et al.) This review gives us incredible insight on, how the scent in the environment and in personal care products can affect our physiology in such a subtle way and transforms physiology. Confirming how vital knowledge of essential oils and their pharmacology is crucial for safe and effective treatments as Aromatherapists.
It was found that the constituent beta-ionone found at trace levels in a typical analysis of Rose Damascena essential oil is a significant contributor to the scent of the floral oil (Shewta et al.) In a study by (Gelis et.al.) beta-ionone has the ability to activate the olfactory receptor (OR51E2) that is found in melanocytes in the skin, signalling melanogenesis and reduce cellular proliferation, which can be beneficial for different skin conditions that involve loss of pigmentation and slow down metastasis in melanoma growths. (Maßberg D & Hatt et al.)
Santalore, a synthetic scent of Sandalwood, activated olfactory (OR2AT4) inducing keratinocytes proliferation and migration which accelerated wound healing. However, it was also determined that natural santalol did not have the same olfactory receptor expression. (Busse et al.)
In the case of citronellal and citronellol, both of these constituents are present in essential oils Geranium, Rose, Eucalyptus Citriodora and Citronella. It was found that these two constituents activate olfactory receptor OR1A2 found in the liver. it was found they can reduce cellular proliferation in the liver. (Maßberg D, et al) the authors concluded in the study that this might be a new gateway to treat certain types of hepatic cancers.
Some studies have indicated that the olfactory receptor OR1G1 found in the gut can detect odorants release such as eugenol found in clove, cinnamon leaf and different chemotypes of basil and bay. The constituent was found to impede serotonin in the stomach - a vital nerve cell that is important for peristalsis in the GI tract. (Braun T et al.) This may explain why aromatherapists have found that the use of the above essential oils benefits gastric upsets.
We are currently in new frontiers of knowledge that olfactory receptors are found in other areas of the body other than the nasal tract.
As an aromatherapist, I believe these findings have an incredible impact in practice - because, this confirms the importance of understanding the risk factors involved with unnecessary exposure on a regular basis, "This also confirms that using essential oils as an environmental entertainment can put people at risk."
However, from a professional perspective, I see skilled aromatherapist have another piece of the puzzle; how essential oils work on the mind and body. With this knowledge at its breakthrough stages of research, we can begin to discover how to integrate the information that is available in practice. By utilizing essential oils as aromatic messengers to activate olfactory receptors throughout the body to trigger physiological changes that lead to homeostasis. At the same time to know when to eliminate an essential oil if is a potential contradiction to what you are treating.
- Braun T, Voland P, Kunz L, Prinz C, Gratzl M. Enterochromaffin Cells of the Human Gut: Sensors for Spices and Odorants. Gastroenterology. 2007;132(5):1890-1901.
- Busse D, Kudella P, Grüning N, Gisselmann G, Ständer S, Luger T et al. A Synthetic Sandalwood Odorant Induces Wound-Healing Processes in Human Keratinocytes via the Olfactory Receptor OR2AT4. Journal of Investigative Dermatology. 2014;134(11):2823-2832.
- Gelis L, Jovancevic N, Veitinger S, Mandal B, Arndt H, Neuhaus E et al. Functional Characterization of the Odorant Receptor 51E2 in Human Melanocytes. Journal of Biological Chemistry. 2016;291(34):17772-17786.
- Gediya S, Mistry R, Patel U, Blessy M, Jain H. Herbal Plants used as cosmetics [Internet]. 2011 [cited 1 December 2018]. Available from: http://www.scholarsresearchlibrary.com/articles/herbal-plants-used-as-a-cosmetics.pdf
- Maßberg D, Simon A, Häussinger D, Keitel V, Gisselmann G, Conrad H et al. Monoterpene (−)-citronellal affects hepatocarcinoma cell signaling via an olfactory receptor. Archives of Biochemistry and Biophysics. 2015;566:100-109.
- Maßberg D, Hatt H. Human Olfactory Receptors: Novel Cellular Functions Outside of the Nose. Physiological Reviews. 2018;98(3):1739-1763.
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