Skip to main content

By Joe Schwarcz, Special to the Montreal Gazette

I try to avoid walking through the ground floor of department stores. I find the cacophony of smells emanating from the various perfume counters literally tear-jerking. My eyes water until I manage to make my escape. It’s an annoying business, but it does make me reflect on the chemistry of the “essential oils” that are the source of many of the compounds floating about. In this case, the term “essential” means that the oil contains the essence of a plant’s fragrance, not that it is in any way essential for its existence or for the existence of any other living organism. Essential oils are used to produce perfumes and to add scent to cosmetics and cleaning products. They are also used as flavourings in foods and beverages and have been used historically as medical treatments by application to the skin, through ingestion or through inhalation, the latter commonly being referred to as “aromatherapy.”

In some cases, as for citrus fruits, the essential oil can be isolated just by mechanical expression, in other words, squeezing of the peel. Solvent extraction is another path to essential oils. Treating plant material with alcohol, hexane or liquid carbon dioxide extracts a mixture of organic compounds that are left behind as the essential oil when the solvent is removed by evaporation. However, the most efficient and widely used method to isolate an essential oil is distillation.

Distillation was introduced sometime during the 12th century and involves heating a mixture of substances and condensing their vapours into a liquid. Compounds with lower boiling points can be separated from ones that do not boil readily. One problem is that many plant compounds decompose at high temperatures. “Steam distillation,” a technique that introduces water or steam into the distillation apparatus, is a way around this problem, given that a mixture of water and organic compounds boils at a lower temperature than either component individually.

The essential oil can be easily separated from the water, because water and oil do not mix.

Now we move on from the science of essential oils to the pseudoscience. And there is plenty of it. Depending on which pseudo-expert has mounted the soap box, either sniffing the right essential oil or rubbing it on the skin can support the immune system, enhance mood, promote sleep, cleanse the body’s organs, boost the libido, ease breathing, foster alertness, treat kidney stones, oxygenate the blood, relieve pain, reduce anger, prevent constipation and, of course, eliminate toxins. If that isn’t enough, essential oils are also reputed to readjust chakras, harmonize bio-electrical frequencies, cleanse negative energies, drive out evil spirits and promote sexual stimulation. In case you are interested, the latter involves massaging the appropriate area with jasmine oil. That is likely to work whether you use an oil or not.

Needless to say, according to enthusiasts, essential oils must be composed only of naturally occurring compounds; synthetics need not apply for inclusion. Why? Because natural substances possess some sort of “life force” absent in synthetics, a claim that was buried two centuries ago with Friedrich Wohler’s demonstration that the urea he had synthesized in the lab was identical to the natural version isolated from urine.

Sales of essential oils are dominated by multi-level marketing (MLM) companies that snare potential participants with promises of wealth through a commission system. Unfortunately, this often drives individuals to make outlandish claims about using the oils to treat cancer, autism, Alzheimer’s disease, mononucleosis or arthritis. There seems to be an oil for any condition that potential customers have. The Food and Drug Administration in the United States has sent warning letters to the major MLM companies, resulting in more careful wording of claims, but there is no way to police what parties say in the privacy of a home, where most sales are made.

Of course, just because some claims on their behalf stink, does not mean that essential oils are useless. The scent of lavender seems to have a calming effect on some people and helps with sleep, but it can cause headaches in others. Peppermint oil may be of some use in indigestion, but that is through ingestion, not inhalation.

Still, further research into aromatherapy may lead to some interesting applications. Alan Hirsch, a legitimate expert in olfaction, measured penile blood flow in 31 male volunteers who were either wearing scented masks or non-odourized masks. The greatest increase in blood flow was seen with the combined odour of lavender and pumpkin pie. And wouldn’t you know it? A company has already jumped on that bandwagon and is marketing “Pumpkin Lavender Perfume Oil.” May be worth an experiment.

There’s no question that a massage with an essential oil or soaking in a scented bath may have a pleasant, relaxing effect, but it is not going to “align your DNA,” “repair your energy field” or “keep your nerves in balance.” Actually, the only thing such claims can do to nerves is fray them. Joe Schwarcz is director of McGill University’s Office for Science & Society ( He hosts The Dr. Joe Show on CJAD Radio 800 AM every Sunday from 3 to 4 p.m.

Source: The Right Chemistry: The science and pseudoscience of essential oils |