Ketones and Toxicity Issues

Sep 27, 12:37 AM

by Katharine Koeppen, RA

Ketone hydrocarbons are neurotoxic, and all essential oils containing ketones should be avoided in situations that require long term use.

This statement is made in pretty much any aromatherapy course that covers basic phytochemistry, and many people buy into it. I certainly did for quite a long time. It's what was drilled into me years ago, and like many aromatherapists, I used high ketone essential oils with great caution.

At first glance, ketones may appear to deserve their reputation as the bad boys of aromatherapy, but this isn't always the case. Not all ketones are neurotoxic; some are quite harmless. For example, sweet fennel (Foeniculum vulgare) and helichrysum (Helichrysum italicum var. serotin) oils contain diketones that pose no contraindications or cautions (Bitter fennel is a very different story, and should be avoided in any aromatherapy application). Carvone, with various isomers present in caraway, dill and spearmint oils, is completely non-toxic. The unique triketones present in manuka (Leptospermum scoparium ct. East Cape) oil are also harmless and are believed to factor into this essential oil's skin-healing properties.

Sage (Salvia officinalis) oil contains a high level of thujone, often in excess of 50%, and it has long gotten a bad rap in aromatherapy books. Thujone is an established neurotoxin, and may have been the culprit responsible for the harmful effects of absinthe, an herbal liqueur that was banned in Europe over 100 years ago. However, virtually all anecdotal data on the use of sage essential oil strongly suggests that the oil itself is not toxic. There appears to be some sort of quenching mechanism in sage oil's phytochemistry.

Other essential oils containing thujone should be used with caution, as should those containing camphor and pulegone. Even menthone, when present in high levels, may cause problems. Blends consisting of high ketone oils should be used judiciously and consistently rotated on and off. Those ketones categorized as toxic are not easily metabolized in the liver and excessive use can cause liver damage and convulsions.

If you are serious about aromatherapy, I recommend having some safety data references in your library. Two frequently recommended sources are Tisserand and Balacs Essential Oil Safety and Watt's Plant Aromatics series.


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