Tea tree and lavender oils may cause enlarged breasts in boys

Feb 1 2007

According to new research the use of shampoos, soaps and lotions which contain lavender oil and tea tree oils can cause some boys to develop enlarged breasts.

It seems they can in some cases upset the hormonal balance and repeated topical use of the products can cause a rare condition called prepubertal gynecomastia, which results in enlarged breast tissue in boys prior to puberty.

Fortunately the changes are not permanent and can be reversed by no longer using the products.

The researchers at University of Colorado and the National Institutes of Health studied three healthy boys, ages four, seven and ten, who developed gynecomastia - all were using shampoos containing the oils.

In each case, several months after the suspected products were discontinued, the gynecomastia had subsided or resolved.

The researchers found by conducting laboratory tests that the oils appeared to mimic estrogen and block the male hormone androgen and they caution parents to be careful of the possible risk.

Ken Korach, Ph.D., chief, Laboratory Reproductive and Developmental Toxicology at NIEHS and author of the study, says doctors who may be seeing patients with gynecomastia need to ask their patients about the products they are using.

It is unknown whether the oils have similar endocrine disrupting effects in prepubertal girls, adolescents or adults.