Sep 6, 10:33 PM

by Katharine Koeppen, RA

Lately I've heard from several practitioners who automatically threw out certain (perfectly good) essential oils after a specified time period because they were afraid of peroxidation. Although it is important to be vigilant about spoilage, this seems to be a fear among aromatherapists which is sometimes unfounded.

Peroxidation occurs when an essential oil is exposed to oxygen over a period of time, causing resinification and a breakdown of the natural chemical bonds in the oil. It occurs most frequently in pine and citrus oils, notably lemon, orange and grapefruit. Essential oils which are extremely high in terpenes, particularly d-limonene, tend to be most prone to peroxidation (over the last few years, the IFRA has issued warnings about high linalool essential oils as well). The deterioration becomes a concern when it causes allergic reactions upon dermal application.

If an essential oil suffers peroxidation, it will be very obvious upon dermal application, even when the oil is applied in a normally safe dilution. An unpleasant prickling or "pins and needles" feeling will be immediately evident, sometimes followed by a stinging or burning sensation of the skin, often accompanied by redness. The degree to which this occurs is dependent upon the sensitivity of the individual and the level of peroxidation. I've experienced this situation firsthand, and believe me, when it happens you'll know it!

If you have an essential oil that has peroxidized, it is no longer safe to use topically. However, this oil can still be used in a diffuser, although the fragrance and therapeutic value will have suffered some deterioration. It is still suitable for deodorizing a room, if nothing else.

Tips on avoiding peroxidation:
You can extend the useful life of citrus and pine oils by refrigerating them, often doubling or tripling their shelf life. If you don't want to refrigerate your aromatherapy cache, at least store it in a cool dark environment. When refilling bottles, tightly cap them as quickly as possible to avoid unnecessary exposure to oxygen. You may want to invest in a container of nitrogen to top off oils that have a short shelf life; the heavy nitrogen gas floats on top of the essential oil, displacing any harmful oxygen in the container.

If an essential oil is suspect, dilute and patch test it first... don't throw out your precious oils unnecessarily!

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