By Dr. Maiko Ochi, N.D., L. Ac.

The scent of freshly cut grass on a hot summer day or of freshly baked chocolate chip cookies … Our sense of smell may trigger pleasant memories, but can it be used as a form of medicine? 

Many conventional doctors may scoff at such a notion.  However, essential oils and aromatherapy have a long history of being used medicinally in traditional cultures throughout the world.

Recent research suggests that there is indeed a physiological mechanism behind the longtime use of essential oils.  Receptors that detect smell, also known as olfactory receptors, are abundant in our noses.  When scent molecules bind to them, a series of biochemical reactions that transmit nerve signals to our brain are set off, and we perceive these as smell.  However, scientists have discovered olfactory receptors in other areas of the body, such as skin, lung, prostate, colon, brain, heart, kidneys, testes, and even sperm.  In fact, genetic evidence suggests that almost every organ in the body has olfactory receptors.

Although it may seem strange that organs besides our nose have receptors that recognize odors, our olfactory system is among the most ancient of the chemical sensors in our body.  Think of these receptors as part of a lock-and-key system.  When a certain molecule fits into its proper receptor, a chain of biochemical reactions that affect physiology are initiated. 

In 2009, researchers at Johns Hopkins discovered that olfactory receptors in mice help to control blood pressure and metabolism.  In 2003, German researchers demonstrated that olfactory receptors on human testicular cells helped guide sperm cells travel to an unfertilized egg. 

If scientists can uncover which molecules bind to which receptors, it may open the door for the development of future treatments for many conditions, from wound healing to cancer.

In 2009, researchers demonstrated that exposing human skeletal muscle to Lyral, a synthetic fragrance that smells like lily of the valley, caused regeneration of these cells, while blocking these receptors inhibited healing.  Earlier this year, researchers in Germany found that human keratinocytes, or skin cells, had olfactory receptors, and that Sandalore, a synthetic sandalwood odor, could bind to them.  Exposing these cells to Sandalore in vitro induced cell proliferation and migration, and regeneration of skin cell layers in a wound scratch test.  Skin healed 30% faster when exposed to Sandalore, which could have significant effects on future treatments for wound healing after trauma and for aging skin. 

In 2009, scientists discovered that beta-ionone from roses and violets inhibited the spread of prostate cancer cells by switching off certain genes. 

In the future, medications that target these olfactory receptors might be developed.  Olfactory receptors are G protein-coupled receptors, which are proteins that are targeted by 40% of all prescription drugs.  However, this night prove to be quite the daunting effort, since there are numerous molecules that can fit into one receptor, and conversely, one molecule can fit into numerous receptors.  Humans have roughly 350 different olfactory receptors (this is on the low end; mice and other animals have over 1000).  It might be better to go the old-fashioned route and use essential oils in the meantime.

Busse D, Kudella P, Grüning NM et al. A Synthetic Sandalwood Odorant Induces Wound-Healing Processes in Human Keratinocytes via the Olfactory Receptor OR2AT4. J Invest Dermatol. 2014 Nov;134(11):2823-32.

Gu X, Karp PH, Brody SL et al. Chemosensory functions for pulmonary neuroendocrine cells. Am J Respir Cell Mol Biol. 2014 Mar;50(3):637-46.

Spehr M, Gisselmann , Poplawski A et al. Identification of a testicular odorant receptor mediating human sperm chemotaxis. Science. 2003 Mar 28;299(5615):2054-8.