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Aromatherapy: Fragrant Medicine or Stinky Pseudoscience?

You may believe that essential oils possess curative powers. Many websites praise the numerous healing properties of these concentrated smelly compounds, from the immune-boosting potential of oregano to the stress-reducing scent of sweet orange oil. These same websites will often provide you with a convenient way of purchasing these elixirs, of course. Why simply inform when you can sell as well? But do these claims smell right to you?

You may believe that essential oils possess curative powers. Many websites praise the numerous healing properties of these concentrated smelly compounds, from the immune-boosting potential of oregano to the stress-reducing scent of sweet orange oil. These same websites will often provide you with a convenient way of purchasing these elixirs, of course. Why simply inform when you can sell as well?

But do these claims smell right to you?
 
Essential oils are called “essential” not because they are needed for life, but because “essential” is the adjective of “essence”, and these oils contain the essence of a plant’s fragrance. They are concentrated and, like any oil, they repel water. The aroma they contain is volatile, which means it turns to gas quite easily at room temperature, allowing it to bind to the receptors in our nose.
 
There is nothing wrong with using these oils to add taste to a recipe or to turn your bathroom into a relaxing spa; but before these oils can be used for medicinal aromatherapy, they would need to be properly tested. You may have heard that some of these oils can kill bacteria. Certainly, in an era in which disease-causing bacteria are becoming more and more resistant to antibiotics, the idea of an all-natural armamentarium against C. difficile is tempting. 
 
The website Natural Living Ideas lists cinnamon oil as one such natural antibacterial agent, but it refers to a study that was done in vitro. Sure, many substances can kill bacteria in a plastic dish, but can they be ingested safely? can they survive digestion? can they be delivered to the right place in the body? can they selectively kill bacteria but not healthy human cells? and can they be sprayed to kill “nearly 99% of airborne bacteria in just minutes”, as Natural Living Ideas claims? There’s a reason why scientists don’t take a basic laboratory finding and deliver it straight to the clinic; the human body is so complex that a potential therapeutic agent needs to overcome a large number of obstaclesbefore it can be used in people.
 
Since these oils are often promoted as relaxing, I thought to myself, “Maybe they can be used for anxiety?” Dr. Michael Greger, a popular health blogger who promotes veganism, produced a video on the use of orange aromatherapy for anxiety. He says it “may have anxiety-reducing properties without the potentially addictive, sedating, and adverse effects” of a drug like Valium. I am all for that. If we can develop or simply discover compounds that are beneficial to our health with little to no side effects, I am sure both doctors and alternative medicine proponents can agree it would be a beautiful thing.
 
Dr. Greger quotes a study done with grad students and concludes, "And the orange did appear to have an anxiety-reducing effect”. I believe this experiment can serve as a great case study of the kind of low-quality research that is often cited by fans of alternative medicine because, as we’ll see, even when the results disagree with their hypothesis, the authors can still conclude that the experiment weighed in their favour.
 
Let’s see if we can spot the two major issues this study has.
 
Firstly, it used a sample of 40 male graduate university students, so whether or not the findings from the study (whatever they turn out to be) can be generalized to the population at large remains to be seen. Moreover, they excluded people with actual psychiatric disorders or with a trait-anxiety score above 48 points on a scale that runs from 20 to 80. This seemingly indicates that students with clinical anxiety were not tested. Once again, even if the results are positive, the authors will not be able to generalize to patients with clinical anxiety.
 
Secondly, the results themselves are simply disappointing. The students were put in a somewhat stressful situation. They were shown names of colours that were written in a different colour. For example, the word “RED” might appear written in yellow, and the student had to quickly say, “Yellow”. They had two minutes to go through a number of these words and they thought they were being watched on a monitor. 
 
Prior to this stress test, they wore a disposable mask with one of three compounds sprayed inside it, one of them being the famed sweet orange oil. Did the students who smelled the orange oil keep it together more than those who sniffed the control oil or the control water? There were two measures of anxiety, both of them questionnaires. On the first measure, there was no difference in anxiety in those who had smelled orange, those who had smelled the control oil, and those who had smelled water. On the second measure, there was an effect of the orange oil, but only for the lowest and the highest concentrations, not the intermediate one, and the numbers were not that different from the water control.
 
Despite these results, the authors conclude the orange essential oil does have anti-anxiety effects! The results themselves do not warrant this conclusion, yet this statement was deemed acceptable to the editor of the Journal of Alternative and Complementary Medicine.
 
These are the kinds of studies put forth by people who want to sell you essential oils for medicinal purposes. If you like the smell of spearmint or lavender, there’s nothing wrong with improving your day by spraying these oils around the house. But beware of the health claims of aromatherapists. They stink of bad science, and the whiff of orange oil will do nothing to fix that.