Monday, June 2, 2008

Tea Tree Oil May Be Used to Treat Scabies

Tea tree oil (TTO; Melaleuca alternifolia) may be used to treat scabies, according to a report published in the May issue of the Archives of Dermatology. Based on an in vitro study and one resistant case that was treated successfully, this may be a readily available and safe topical alternative.

"The essential oil of the tea tree is an Australian Aboriginal traditional medicine for bruises, insect bites, and skin infections," write Shelley F. Walton, PhD, from the Menzies School of Health Research in Darwin, Australia, and colleagues. "Studies have demonstrated its antimicrobial activity against gram-positive (eg, Staphylococcus aureus), gram-negative (eg, Escherichia coli), yeast (eg, Candida albicans), and viral (eg, herpes simplex viruses) organisms, but there is little information on its antiectoparasitic activity."

This study determined the in vitro activity of 5% TTO and some of its individual active components against Sarcoptes scabiei var hominis mites collected from a 20-year-old Aboriginal woman admitted to the Royal Darwin Hospital with crusted scabies.

The 5% TTO and its active component terpinen-4-ol were highly effective in reducing mite survival times, and there were statistically significant differences in mite survival curves for 5% TTO, 2.1% terpinen-4-ol, 5% permethrin, and ivermectin (100 µg/g of Emulsifying Ointment British Pharmacopoeia 88 [BP88]). The patient was successfully treated with topical 25% benzyl benzoate containing 5% Tea Tree oil in combination with oral ivermectin, both in multiple doses.

With 5% Tea Tree oil, all scabies mites were dead within three hours, whereas terpinen-4-ol alone required 11.5 hours for 100% mortality. The effect of terpinen-4-ol alone on reducing viability of the scabies mites was similar to that when combined with alpha-terpineol and 1,8-cineole. These components used alone were relatively inactive against the scabies mite, suggesting that terpinen-4-ol is the active component. After one hour of exposure, only 10% of mites tested against 5% permethrin and ivermectin, and none of the mites tested against the Emulsifying Ointment BP88 were dead.

"Documentation of resistance against antiectoparasitic compounds is increasing. Reported S scabiei treatment failures with lindane, crotamiton, and benzyl benzoate, as well as likely emerging resistance to 5% permethrin and oral ivermectin, are of concern and advocate for the identification and development of novel acaricidal drugs," the authors write. "The results suggest that TTO has a potential role as a new topical acaricide and confirm terpinen-4-ol as the primary active component."

The Channel 7 Children's Research Foundation of South Australia, Adelaide, and the Cooperative Research Centre for Aboriginal and Tropical Health, in Darwin, Northern Territory, supported this study. The authors report no relevant financial interest in this article.

Arch Dermatol. 2004;140:563-566

Reviewed by Gary D. Vogin, MD