Hello! Thanking you in advance for your time…I have a question regarding something that I read about peppermint and eucalyptus oils increasing the skins absorption of 5-fluorouracil, an anti-cancer drug. The study cited was Abdullah et al 1996, Williams & Barry, 1989. I am unable to find that particular study and wondered if you have any input as to the validity of this statement. If this is indeed true…do you have any special recommendations for those with cancer, undergoing chemotherapy or for those taking cancer relapse prevention drugs?
With great regard, Tiffany

Hi Tiffany,

A number of essential oils enhance the transcutaneous penetration of other substances. This is a widely-studied phenomenon, and research is ongoing. It happens because some essential oil constituents are very good at crossing the epidermis. In a 1991 paper, Williams and Barry found that 1,8-cineole, the major constituent of eucalyptus oil, enhanced the skin permeability of 5-FU by an incredible 95 times.

5-FU is only applied to the skin to treat skin cancers. In those situations, it would be prudent to avoid applying any essential oils or aromatherapy products to the same area of skin. When 5-FU is given intravenously (for internal tumors) applying essential oils to the skin will have no effect. Similarly, ingested essential oils will not affect the dermal delivery of 5-FU, or any other substance.