Lavender Oils May Arouse Breast Woes in Young Boys

January 31, 2007

DENVER -- Three cases of prepubertal gynecomastia have raised red flags about the estrogenic-like and anti-androgen effects of tea tree oil and lavender, two popular additives in soaps and lotions.

DENVER, Jan. 31 -- Three cases of pre-pubescent gynecomastia in young boys have raised red flags about the estrogenic-like and anti-androgenic effects of tea tree oil and lavender, two additives in soaps and lotions.

Gynecomastia at puberty is common -- about 60% of boys are affected -- but it is rare before puberty and is usually considered pathological, according to Clifford Bloch, M.D., of the University of Colorado School of Medicine.

But in these cases, the culprits were popular soaps, shampoos, and lotions containing the oils, Dr. Bloch and colleagues reported in the Feb. 1 issue of the New England Journal of Medicine.

"Since there was no identifiable cause for prepubertal gynecomastia in the three patients we reported," Dr. Bloch said, "we speculated that environmental factors might be contributing to their condition."

The first clue, he said, was that stopping the use of the various products caused the enlarged breasts to return to normal within a few months.

To confirm that idea, researchers from the National Institute of Environmental Health Sciences (NIEHS) in Research Triangle Park, N.C., conducted a series of in vitro tests on both oils.

The results "confirm that pure lavender and tea tree oils can mimic the actions of estrogens," said Ken Korach, Ph.D., of the NIEHS. Also, he said, the oils inhibit the effect of androgens.

"This combinatorial activity makes them somewhat unique as endocrine disruptors," Dr. Korach said.

In the three reported cases -- four, seven, and 10 year old boys -- all had normal serum concentrations of endogenous steroids and none had been exposed to any known outside endocrine disruptors, such as medications, oral contraceptives, marijuana, or soy products, Dr. Bloch and colleagues reported.

The finding should alert doctors treating young boy who present with gynecomastia, said pediatric endocrinologist Henry Anhalt, D.O., of St. Barnabas Medical Center in Livingstone, N.J.

"Tea tree oil and lavender oil and a whole host of other herbal products have been identified to have primarily estrogen-like activity," Dr. Anhalt said, and should be avoided.

In pre-pubescent boys, gynecomastia is often associated with estrogen-producing tumors, so "the search for the cause becomes something of great urgency," said Dr. Anhalt, who was not involved with the study.

He said physicians need to be aware of the possibility of endocrine disruption in their patients, especially because in some cases it may cause changes in DNA in the germ cells.

Echoing Dr. Anhalt's comments, Dr. Korach said: "We want to encourage doctors who may be seeing patients with gynecomastia to ask their patients about the products they are using."

He added that while the association has been confirmed, it's not known how strong the effect is. "Further research is needed to determine the prevalence of prepubertal gynecomastia in boys using products containing lavender and tea tree oils," Dr. Korach said.