By Robert Tisserand

Note: below is a link to a full article, along with an Executive Summary in six languages.

Nature is complex. A single essential oil can contain dozens of constituents, each one of which, alone, has certain properties. How do we make sense of such complexity in nature? We often turn to patterns, to broad categories, just to give us a “rough idea” of what’s going on. And sometimes this works well enough. But what if our “rough idea” is more wrong than right? You may not realize it, but much of the information taught and written about concerning essential oils is based on a flawed idea called Functional Group Theory (FGT).

Essential oil constituents can be categorized according to their functional group, or chemical family. Such categories include alcohols, aldehydes, ketones, esters, phenols and more. For some 30 years, FGT has been used as a shortcut to understanding the actions of essential oils in the body. Students learn the properties of each functional group, which essential oils are high in which molecules, and which functional group each molecule belongs to.

However, while this categorization makes sense in terms of chemistry, it turns out that it is not an accurate way to predict or describe the therapeutic properties of essential oil constituents. This is partly because FGT was originally based on a long-debunked hypothesis, and partly because current research shows that the properties of essential oil constituents do not fall into such neat categories.

Marco Valussi, Andrea Cont, Joy Bowles and I spent two years writing a comprehensive explanation for why FGT is not a useful tool to learn or predict essential oil properties. Instead, we propose an approach that more accurately reflects the science and that is, in the end, simpler. Studying the properties of constituents can be extremely useful, but these should be studied individually, rather than in (functional) groups. Abandoning FGT does not mean the therapeutic activities of a constituent need to change, so long as they are based on evidence of effect, and not on assumption.

Robert Tisserand
Robert Tisserand is a speaker, educator and consultant on the science and benefits of essential oils and their safe and effective application, and in 1977 he wrote the first English language book on aromatherapy. In addition to teaching online courses, in recent years he has inspired live audiences in Europe, Asia, North America and South America. He was privileged to receive a Lifetime Achievement Award from the AIA in Denver in 2007, and in 2014 he co-authored the second edition of Essential Oil Safety, which has helped set industry safety standards. Robert is the principal of The Tisserand Institute.