Topical use of lavender or tea tree oils may lead to prepubertal gynecomastia, according to a report in the New England Journal of Medicine Volume 356:479-485February 1, 2007 Number 5.
Researchers present the case histories of three boys -- aged 4, 7, and 10 -- with prepubertal gynecomastia; all were otherwise healthy. None of the boys had been exposed to known exogenous endocrine disruptors such as medications, oral contraceptives, marijuana, or soy products, but each was using lotion, soap, shampoo, balm, or styling gel containing lavender oil, and in some cases tea tree oil, when gynecomastia developed. Each boy's symptoms resolved after such use was discontinued, and subsequent cell-culture studies showed both oils to have estrogenic and antiandrogenic activities.
Physicians "should be aware of the possibility of endocrine disruption and should caution patients about repeated exposure to any products containing these oils," the researchers write.