Published 10 Apr 2018
Essential oils have been used by humans for centuries for their huge array of natural benefits. They’ve been used to treat illness, alleviate pain, and for their spiritual and mood-altering effects, but while the physical benefits are easy to test, proving their psychological effects is a little trickier.
Head of Psychology at Regent’s University, and author of The Neuropsychology of Smell and Taste, Neil Martin explains that, while tests have been done on the brain as well as the essential oils themselves, we only have clues to how and why scent can affect our moods and behaviours.
Aromatherapy is one of the ways people have used essential oils in recent history, with its advocates claiming it works wonders for a wide range of problems, including altering your mood and general outlook on life. But the question is: can it? Neil explains: “There are so many confounds. Aromatherapy includes massage, but also music and other people - that’s not strictly ‘aroma’ therapy. It is not simply looking at the effect of the aroma on behaviour; it is the aroma in combination with other things, and it could be the other things that have this effect.”
Neil suggests that to test the effects of essential oils objectively, each aroma must be separated out and tested individually to see if it brings about the effects and claims attributed to it.
In fact, to prove this theory he carried out a test using lemon oil to determine how effective it was at muting our response to pain. What his tests found was that lemon actually heightened people’s perception of the pain they felt - contrary to what many aromatherapists claim. However, Neil points out this doesn’t prove that essential oils cannot alleviate pain, instead that lemon oil cannot do so alone. Perhaps there’s more at play when we sniff or use an essential oils than our bodies’ chemical reactions. Our brains and psychology have a lot to answer for when it comes to our reaction to smells.
The psychology of scent
Smell, more than any other sense, is connected to our memories and emotions. Just one whiff of a scent can transport you to a different place, time and even mood – but why is this?
One school of thought is that the reason we perceive essential oils like lavender as a calming is a result of cultural conditioning. It sounds sinister, but it means that culturally we have come to associate lavender with relaxation because perhaps our parents scented our pillows with lavender when we were children to help us sleep.
There is evidence to suggest that this kind of cultural learning is all that is required for a smell or essential oil to be effective.
In other words, it’s not necessarily the essential oil that brings on a desired effect, but our own expectation of the essential oil.
Neil explains: “If you give people the same odour and you either call it ‘cheese’ or ‘body odour’, their psychological response to the same odour differs. The brain changes as well. It is as if the label you give to something changes the way the brain processes that particular odour.
“What is even more interesting is that the brain also responds in a way that is consistent with the label. So if you think a smell is unpleasant, that part of the brain responsible for unpleasantness will become active. It is as if the brain processes this as an unpleasant stimulus and those parts of the brain become activated.”
The scent methyl salicylate, otherwise known as wintergreen, is another slightly less-pungent example. In the UK it was used in medication in the 1960s, while in America it is used in peppermint sweets. If you ask a British person to rate the smell of wintergreen in terms of pleasantness they give it a low score, whereas if you ask an American, it scores quite highly. This goes to prove how important cultural learnings and individual expectations and associations are to the perception of smell.
Unlike the other senses, the key response to smell is emotional. Neil explains that this could be because olfactory information does not pass through the same sensors before it reaches the brain as the other senses do, making it a more emotional, primal sense.
Another reason he suggests, is that we have a distinctly poor language when it comes to describing smell. He says: “Liking or disliking is the dominant psychological reaction to smell. It’s not like anything else. When you look at something you immediately understand it is a door, or a bag. Your first thought is not related to whether you like or dislike it.
“But with smell it is. We don’t have a language for scent because it is chemistry. We don’t think ‘Oh we love the smell of hexanol in the afternoon’; we say ‘We like the smell of freshly cut grass’. Because we are quite poor at naming odours our immediate reaction to them is emotional.”
With all these factors to consider, it’s easy to see why it is difficult to pinpoint what makes an essential oil make you feel good. Is it psychological, physiological, a placebo, or a combination of them all? But, until someone figures it out, it makes sense to just roll with what feels good. After all, experience is a type of science, and centuries of safe and continued use seem a good reason to believe in the power of essential oils, even if the exact facts are a little more difficult to piece together.