If you use organic or nonorganic essential oils at home, be advised of a study published in a January edition of the New England Journal of Medicine. Researchers found repeated topical use of products containing lavender oil and/or tea tree oil may cause “prepubertal gynecomastia” (enlarged breast tissue in boys who have not yet reached puberty).  

Scientists at the National Institute of Environmental Health Sciences (NIEHS) confirmed what the reporting University of Colorado pediatric endocrinologist found after diagnosing three young male patients: an association between product use and development of the disorder. These three otherwise healthy boys, ages 4, 7 and 10, had normal hormonal levels when diagnosed, but each had used either lavender-scented soap and skin lotions, or shampoos or styling products that contained tea tree and lavender oil as ingredients. Once products were discontinued, each boy’s gynecomastia subsided or resolved.

“Patients with prepubertal gynecomastia may want to consider reducing the use of products that contain these oils,” says Ken Korach, PhD, chief of Laboratory Reproductive and Developmental Toxicology at NIEHS. “Although we found an association between exposure to these essential oils and gynecomastia, further research is needed to determine the prevalence of prepubertal gynecomastia in boys using products containing lavender and tea tree oils.  Results of such epidemiological studies are important to tell us how strong the association is between topical application of the oils and prepubertal gynecomastia.”

Dr. Korach says pure lavender and tea tree oils “can mimic the actions of estrogens and inhibit the effects of androgens.” It’s unknown whether these oils have similar endocrine-disrupting effects in prepubertal girls, adolescents or adults. Endocrine disruptors are naturally occurring compounds or synthetic chemicals that may interfere with the production or activity of hormones of the endocrine system, leading to adverse health effects.