How Scent Affects Us
Our sense of smell is the main modality by which we experience the world around us; however we underestimate its significance. Only in recent years have researchers begun to unlock the complexities that make up the sense of smell and have reported that smell sensitivity is more significant than previously predicted. In fact, our sense of smell is directly linked to our physical and mental health profiles.

Smell is Intimately Linked with Memory
One reason is that the olfactory bulb, the part of the brain that processes smell, interacts with regions of the brain that are responsible for storing emotional memories. Through the process of conditioned learning, a smell becomes associated with the particular experience, person, or time period with which it is repeatedly paired. In some cases, we may not be aware of a specific memory, we just have a positive or negative association with a smell and don't know why. Research suggests that some smell preferences, like an affinity for alcohol, junk food, and garlic, may even develop in the womb.

Smell Impacts Our Mood
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.

Some smells, vanilla in particular, are almost universally liked (research suggests that vanilla has calming properties). These pleasant smells improve our mood, but also sometimes impair our judgment. Certain good smells, however, like peppermint and lemon, seem to sharpen reasoning and improve work performance.

Smell is an Essential Element of Attraction
Research suggests that humans subconsciously pick up on potential mates' pheromones, hormones that can travel outside of the body and are detected through smell (pheromones are what dogs are smelling when they sniff each other's butts; it's still unclear to what extent humans rely on pheromones). Some studies suggest that pheromones contain information about fertility and genetic compatibility. In one much publicized but controversial study, female participants sniffed sweaty T-shirts worn by men they had never met, and their preference ratings indicated that they preferred the scent of men whose MHC (major histocompatibility complex) genes were different from their own, a combination that can give offspring a stronger immune system. These findings suggest that people might literally be able to sniff out their ideal mate, but the evidence for this effect has been mixed. Patterns of attraction are also dependent on where women are in their menstrual cycle and whether or not they are on the pill.

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. Essential oils are a rich mixture of volatile aromatic compounds. Aroma in a “chemical” sense means that individual compounds (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 affect us in different ways.

There are many acceptable ways to use essential oils for their aromatic properties. One method is to diffuse the oil into the air. Diffusion makes the oil accessible to the body and research indicates that there is 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 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.

Lastly, don't underestimate your sense of smell. It has the power to bring you back to childhood and closer to far-away loved ones, to make you feel happy, alert, and comforted, to keep you safe from danger, and possibly even to help you find love.

REFERENCES
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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.
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