We all know that smells can affect the way we feel. Indeed, essential oils are used regularly in Ancient Egypt and India as an adjunct to improve health and well-being. These oils are usually extracted by steam distillation from fragrant plants such as lavender, rose, orange, cinnamon or peppermint, to name just a few. The oils can be inhaled, used during massage, or even ingested.
It is theorised that the effect scent has on mood may be mediated by the architecture of the olfactory system. The areas of the brain that process scents are directly connected with areas involved in processing emotions, memories and autonomic responses.
Let’s start from the beginning, i.e. the nose. Here the receptors on olfactory neurons detect odorants (chemicals which form a scent) and transform these particles into electrical signals. These signals travel along the olfactory nerve to the olfactory bulb in the central nervous system (Kadohisa, 2013). The olfactory bulb forms connections with other brain areas such as amygdala (the center of emotions) (Wilson-Mendenhall et al., 2013) and the entorhinal cortex (important in memory) (Takehara-Nishiuchi, 2014). The amygdala, in turn, is connected to the hypothalamus, a part of brain that regulates physiological states, e.g. controlling the release of stress hormones. This is one reason why smells can have an impact on our mood and why they evoke such strong memories. Can you think of any smell which conjures up a memory for you? – If so, let us know in the comments below!
A number of people find that essential oils can affect their mood but these are not the only odorants can which have this effect. If you like spending time in nature you probably noticed that being surrounded with vegetation can reduce stress. One study suggests that the “green odour” (the scent of leaves and vegetation) changes the electrical signals in our brain in a way that brings about a sedative-like action, reflected in a feeling of relaxation (Sano et al., 2002). Studies on rats have shown that this effect could be due to the action of the green odour on the brain circuit which release adrenaline and cortisol (the hypothalamic-pituitary-adrenal axis) (Nakashima et al., 2004).
Another botanical scent, the essential oil of rose, may have a similar effect on the brain’s stress circuitry (Fukada et al., 2012). Women who carried a test paper soaked in rose essential oil for several days during exam period showed no change in their cortisol levels, while those students supplied with a jasmine aroma patch or nothing at all, had increased amount of cortisol around their exams. One suggestion raised by this study is that rose essential oil could prevent the release of stress hormones. Further, in another study essential oil extracted from orange peels reduced the activity in the prefrontal cortex, part of the brain involved in integrating information, planning and making decisions (Igarashi et al., 2014). After barely ninety seconds of inhaling these oils participants felt more “comfortable”, “relaxed” and “natural”.
Have you ever noticed that in times of stress your skin becomes dry or you are plagued by eczema? Stress causes shrinking of the lipids that form the protective skin barrier, increasing transepidermal water loss (TEWL) – the escape of moisture from the skin. Some studies suggest that inhaling the “green odour” or rose essential oil can reduce this water leakage and prevent the stress-related drying of the skin (Fukada et al., 2007).
Aromatherapy is based on a holistic approach to the patient, considering both their physical and psychological needs (meaning that any effects of aromatherapy may be person-specific). Scientific studies have shown evidence both for and against the effectiveness of aromatherapy but with many individuals reporting benefits further research is certainly required.
This article is for informational purposes only. Always use essential oils as instructed by the manufacturer or a therapist.
Post by: Jadwiga Nazimek
Fukada, M., E. Kano, M. Miyoshi, R. Komaki, and T. Watanabe, 2012, Effect of “rose essential oil” inhalation on stress-induced skin-barrier disruption in rats and humans: Chem Senses, v. 37, p. 347-56.
Kadohisa, M., 2013, Effects of odor on emotion, with implications: Front Syst Neurosci, v. 7, p. 66.
Nakashima, T., M. Akamatsu, A. Hatanaka, and T. Kiyohara, 2004, Attenuation of stress-induced elevations in plasma ACTH level and body temperature in rats by green odor: Physiology & Behavior, v. 80, p. 481-488.
Sano, K., Y. Tsuda, H. Sugano, S. Aou, and A. Hatanaka, 2002, Concentration effects of green odor on event-related potential (P300) and pleasantness: Chemical Senses, v. 27, p. 225-230.
Takehara-Nishiuchi, K., 2014, Entorhinal cortex and consolidated memory: Neurosci Res, v. 84, p. 27-33.
Wilson-Mendenhall, C. D., L. F. Barrett, and L. W. Barsalou, 2013, Neural Evidence That Human Emotions Share Core Affective Properties: Psychological Science, v. 24, p. 947-956.
5 thoughts on “Aromatherapy: what is it and does it actually work?”
Nice article. I’ve been studying for quite some time why aromatherapy works, and have recently come upon an interesting theory. Would enjoy others’ opinions on the subject.
Just as there is sodium chloride in animals’ cells, most probably in relationship to our early evolution from the oceans, our later evolution in the forests and savannas would lead to an environment in which the secondary metabolites of plants, such as terpenes and terpenoids were very prevalent for millions of years.
Animals evolved, and developed their homeostatic mechanisms, while breathing in these terpenes. It is well known that many terpenes are anxiolytic, that is they lower anxiety levels.
Maybe it is the lack of terpenes in our daily breath that leads to an increase in anxiety, and it is the replacement of these naturally occurring terpenes, through aromatherapy, that brings us to the natural state of lowered anxiety.
I’ve elaborated upon this a bit more here: https://monq.com/why-does-aromatherapy-work/
As above, I’d be interested in hearing your thoughts on this theory.
Are you saying that there is placebo controlled, double blind evidence for essential oils? It was unclear.
Eric, I think that’s really interesting.
Michelle, Fukada’s group (2012) studied rats, which they divided into 4 groups: vehicle (equivalent to placebo) + stress, rose + stress, control and rose. Double blinding with essential oils is tricky due to their characteristic smells. In the human study of the same group participants were randomly assigned to groups: rose + stress and vehicle + stress (control). They also did an additional experiment with jasmine oil as control in addition to placebo.
There are some other randomized controlled studies, e.g. this one:
Seol, G. H., Y. H. Lee, P. Kang, J. H. You, M. Park, and S. S. Min, 2013, Randomized controlled trial for Salvia sclarea or Lavandula angustifolia: differential effects on blood pressure in female patients with urinary incontinence undergoing urodynamic examination: J Altern Complement Med, v. 19, p. 664-70.
There is an old perfume called Tabu. When I was a little girl in 1963 I was traveling by ship to Okinawa with my mother and sister to meet up with my father who was stationed there with the military. The voyage was about 2 weeks. I apparently sat beside a woman at dinner who wore this perfume. The perfume is apparently still around because whenever I get a whiff of it, it takes me back to that trip on the ship. Great memories!
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