Dr. David K. Hill, CMO, Chairman of the Scientific Advisory Board Our sense of smell is the frontline modality by which we experience the world around us; however, many people may underestimate its significance. By comparison, humans have a weaker sense of smell than many animals, which must use smell for sustaining basic life functions (tracking food, identifying a mate, etc.). Although your nose may not be as acute as that of a bloodhound, you can still detect thousands of varieties of odors in infinitesimal quantities. Only in recent years have researchers begun to unlock the complexities that make up the sense of smell and, in turn, have reported that smell sensitivity is actually much more significant than previously predicted. In fact, our sense of smell is directly linked to our physical and mental health profiles. The Aroma of Essential Oils When it comes to essential oils, their powerfully fragrant aromas are the first thing we notice as we unscrew the bottle cap. By definition, essential oils are a rich mixture of volatile aromatic compounds. Because of their volatility, aroma is actually an intrinsic feature to essential oils, or in other words, essential oils are their aroma. Aroma in a “chemical” sense means that individual compounds (in this case, essential oil constituents) are able to interact with olfactory (smell) receptors in the nose. Not every type of compound elicits an aroma, because the compounds have to be very small and readily evaporate into the air. Essential oil compounds meet both of these criteria and are able to quickly and easily bind to smell receptors in the nose. The chemistry of essential oils varies widely from oil to oil, which explains why essential oils possess such widely different aromas, and thus, affect us in different ways. How Scent Affects Us One of the most well-studied areas of aroma research is the effect of smell on emotions and mood. For example, there is convincing evidence demonstrating that simply inhaling the aroma of an essential oil is effective for calming nervous or anxious feelings in a variety of settings. The smell receptors located on the upper surface of the nasal cavity make direct links with the limbic system of the brain, an area that governs the body’s emotional responses. This close connection between aroma and emotion becomes obvious in our everyday life as certain odors trigger memories or specific feelings. Some aromas directly impact mood (for example calming, balancing, or invigorating), while others trigger memories of a specific experience, often one tied to a strong emotion. Intriguing new research has also helped us recognize that the benefits of aroma extend far beyond just emotional regulation. In addition to influencing the limbic region of the brain, olfactory centers are also intricately linked with the hypothalamus, an area of the brain more familiarly nicknamed the “visceral control center” because it controls physiologic functions throughout the body. The hypothalamus exerts its powerful influence by interacting directly with the pituitary gland, or “master gland,” a small gland located in the brain. The pituitary gland secretes hormones involved in the regulation of blood pressure, hunger and thirst signals, thyroid function, sleep cycles, production of sexual hormones, and memory, among other things. Because of the direct link of the olfactory system to this area of the brain, aroma is capable of interacting directly with the hypothalamus, influencing neurochemistry throughout the body, and, in turn, potentiating powerful health outcomes. There are many acceptable ways to use essential oils for their aromatic properties. One method is to diffuse the oil into the air. Not only does diffusion make the oil accessible to the body, but research indicates that there are also air purification benefits when diffusing oils. When diffusing oils, use of cold air or hydrodiffusion is best because burning or heating essential oils can alter their delicate chemistry. If a diffuser is not available, simply dropping essential oils into the palm of the hand and then cupping around the nose and breathing deeply is a convenient method for using essential oils at any time, in any situation. Although there are many ways that essential oils can be applied, throughout my experience as a physician, I have found that repeated daily exposure to the aroma of essential oils provides unique and significant support to healthy function of the body and mind. REFERENCES Ceccarelli I, Lariviere WR, Fiorenzani P, et al. Effects of long-term exposure of lemon essential oil odor on behavioral, hormonal, and neuronal parameters in male and female rats. Brain Res. 2004;1001 (1-2):78-86. Conrad P, Adams C. The effects of clinical aromatherapy for anxiety and depression in high risk postpartum woman – a pilot study. Complement Ther Clin Pract. 2012;18(3):164-168. Fayazi S, Babashahi M, Rezael M. The effect of inhalation of aromatherapy on anxiety level of patients in preoperative period. Iran J Nurs Midwifery Res. 2011;16(4):278-283. Inouye S, Uchida K, Yamacuchi H. In-vitroand in-vivoanti-Trichophyton activity of essential oils by vapour contact. Mycoses. 2001. 44:99-107. Lehrner J, Eckersberger C, Walla P, et al. Ambient odor of orange in a dental office reduces anxiety and improves mood in female patients. Physiol Behav. 2000;71(1-2_:83-86. McCaffrey R, Thomas DJ, Kinzelman AO. The effects of lavender and rosemary essential oils on test-taking anxiety among graduate nursing students. Hollist Nurs Pract. 2009;23(2):88-93. Posted on May 27, 2015.