One of the most frequent conversation starters in the aromatherapy community is “what does it smell like?” One of the most frequent answers is, “Oh, …I can’t really describe it!”.
Previously, it was thought that the human nose could only detect 10,000 scents. But in 2014, neurobiologist Leslie Vosshall of Rockefeller University in New York City, led research that found that the human nose is able to smell a trillion scents, with varied individual responses. The researchers calculated that the least successful smeller in the study would be able to smell only 80 million unique scents. And the best performer had a far more sensitive sense of smell, likely able to distinguish more than a thousand trillion odors. (1)
Ironically, even though we can smell them, we aren’t always able to identify or describe them. Part of the equation, of course, is prior experience. If we haven’t come into contact with a certain aroma before, there is obviously no way we can identify it. But there is another element involved that the human nose simply has difficulty doing – deconstructing scent. For example, Robert Tisserand cited that “Essential oils typically contain dozens of constituents with related, but distinct, chemical structures.” (2) How many could pick out each and every constituent from one oil? What if it were a blend of multiple oils, with similar, but not quite the same, constituents?
As in the example of peanut butter, given in PBS article “Why We’re Good at Identifying Smells, But Horrible at Describing Them”, roasted peanuts give off roughly 200 air molecules, peanut oil, 100. (3)
In an experiment at Northwestern University, participants were fed a large amount of peanut butter, they were then asked to describe peanut butter. Scans indicated a change in neural activity in the region of the brain designed to identify odors and associating them with similar smells – the posterior piriform cortex. This is the first stop that olfactory information makes in the brain after the olfactory bulb, suggesting that a decrease in a smell’s value may start at the level of perception. Participants reported finding the smell of peanut butter less pleasing after having eaten such a large amount of it. (3) I recently asked Mark Webb how people can claim to love the smell of coffee report disliking the taste. Mark explained to me that coffee contains bitters that we are not able to smell.
Likewise, there is the connection between smell and memory/emotion. If a scent evokes a pleasant memory, perhaps a grandmother’s lavender scent or baking cookies, this will be a pleasant memory/emotional response. I’ve often mentioned the natural gas sub station near my home that every time I pass it and breath in, I am reminded of being at my great-grandmother’s house – 45 years ago. So while that pungent odor is repelling to many, it tickles my subconscious to remember a special person, long gone. A strong floral aroma may remind some of working in their garden or a gift from an admirer, while for others, it may trigger emotions left over from a loved one’s funeral.
Some have asked why they “taste” essential oils while pouring, without ever having put the oil in their mouth. This is because the two senses are actually interactive. Both are considered “chemsensations”, occurring when molecules are released, stimulating nerve endings in the nose, mouth or throat. These cells transmit data to the brain, where tastes and smell are identified. Olfactory cells, found in a tiny patch of tissue high up in the nose, are stimulated by odor. Gustatory cells, clustered in the taste buds of the mouth and throat, react to taste mixed with saliva. Some of the tiny bumps that can be seen on the tongue contain taste buds. All send messages to the brain of what they are experiencing. (4) As these areas are so close together and interactive, molecules that we breath in, Mark Webb explains, can pass over the taste receptors as well.
When, for example, nasal congestion sets in, there is an interruption of air flow passing over the olfactory receptors, preventing odorous compounds from reaching them, interrupting our sense of smell. Although the stimulation of taste receptors is not affected, the loss of smell alters the flavors we perceive. (5)
I recently mentioned someone else’s description of an essential oil as “sweet, woody.” Imagine my reaction when her only response was “PICKLES!!” So the next time you ask, “What does that smell like?” remember that smell is not always unbiased. It is strongly affected by experience, memories and emotion.
My comments: We see this in some clients reactions to products. I have seen long conversations on Facebook when someone has referred to a product as smelling like "cat pee" and other will jump in stating how lovely it is. Which indicates to me that the same aroma will be experienced differently by different people, above and beyond the emotional triggers Sandy mentions above.
Another issue when it comes to describing the aroma of a specific oil or botanical is that our society ignores olfactory stimulus, and we haven't developed the language to accurately describe the fine differences between, for example, Cedrus atlantica and Cedrus deodara. I know that in writing about our products I am forced to use the language of music, of color, of flavor, to describe, in our language, doesn't exist.