Although essential oils are absorbed through the skin into the blood stream somewhat more readily when applied undiluted than when used in diluted form, this is not a good practice because the risks of experiencing skin irritation and sensitization (a type of allergic reaction) increase greatly when undiluted essential oils are put on the skin and the risk of systemic toxicity and drug interactions also increases. I want to repeat that because it’s important – using undiluted essential oils on the skin substantially increases the risk of skin irritation and sensitization reactions and also increases the risk of systemic toxicity and drug interaction.
Risk of Systemic Toxicity
While the risk of systemic toxicity from reasonable external application of the essential oils used by responsible aromatherapists is very low, the occurrence of skin sensitization reactions has been increasing in the United States as a few companies here have irresponsibly recommended the topical use of undiluted essential oils. Even lavender essential oil, which was once considered by most aromatherapists to be safe for undiluted use, is now being found to produce sensitization in some individuals, apparently as a consequence of over-use in undiluted applications.
Not everyone who uses undiluted essential oils will develop sensitization reactions, and those who do will generally only have problems after repeated use of the same undiluted oil. However, for those unfortunate people who do experience these often avoidable reactions, the experience can be very distressing as it can be accompanied by severe itching that lasts for days. This may leave the affected individual more likely to develop such reactions to other topically applied substances in the future. Why would anyone want to take such risks when diluted essential oils are much safer and work very well to achieve the desired therapeutic effects?
Reasonable Dilution Rates
Here are reasonable dilution rates for several methods of topical use of essential oils:
| Procedure | Recommended Range of Essential Oil Concentration |
|---|---|
| Full-body Massage | 1.5 – 3% |
| Facial Care | 0.2 – 1.5% |
| Bath & Body Products | 1.5 – 4% |
| Wounds / Necrotic Skin Ulcers | 5 – 15% (on a small area) |
| Localized Pain | 5-15% |
| Other Localized Issues | 3-10% |
These are general guidelines and extra care must be utilized with essential oils that are known to be sensitizing, irritating and/or phototoxic, some of which have specific maximum dermal concentration levels. Information on maximal dermal concentrations for essential oils of such types can be found in Tisserand and Young’s reference book on essential oil safety.
