Tea Tree Oil and Lavender Linked to Breast Tissue Development in Prepubescent Boys

According to the National Institutes of Health, the New England Journal of Medicine has released a study that links the use of tea tree oil and lavender to breast development in prepubescent boys. The condition is known as prepubertal gynecomastia, and is extremely rare.

The study was completed at the National Institute of Environmental Health Sciences (NIEHS) after Dr. Clifford Bloch, a pediatric endocrinologist at the University of Colorado, diagnosed three boys ages 4, 7, and 10 with prepubertal gynecomastia. All three boys had normal hormone levels at the time of diagnosis. Dr. Bloch states, "Since there was no identifiable cause for prepubertal gynecomastia in the three patients we reported, we speculated that environmental factors might be contributing to their condition." The common factor in all three of the cases was the use of products containing lavender and tea tree oils. He recommended that the boys discontinue the use of these products, and within a few months the gynecomastia had resolved.

Dr. Bloch contacted Ken Korach, PhD at the NIEHS to discuss the cases. Korach is the chief of the Laboratory Reproductive and Developmental Toxicology at NIEHS. Korach agreed to conduct experiments on human cells in order to determine if the essential oils were endocrine disruptors. It was determined through the experiments that both lavender and tea tree oil mimic the actions of estrogen in the body, the hormone that stimulates the growth of breast tissue. The researchers also determined that the oils inhibited the effects of androgen. Androgen is a hormone that inhibits the growth of breast tissue and determines male characteristics. This combination of effects may cause breast development. These essential oils, which are very popular in baby products as well as soaps and shampoos, may be labeled as endocrine disruptors since they have caused an imbalance of hormones, causing adverse health effects.

After testing, it was determined that the boys should not have any long term effects. The use of the oils did not change levels of the usual form of estrogens and androgens circulating in the body.