Lavendar and tea tree oils
mimic estrogen
UPdate Summer 2007

Personal care products containing tea tree and lavender oils can cause breast development in pre-pubescent boys according to a recent study.

The discovery came about after an endocrinologist, Dr. Clifford Bloch, saw five boys with this unusual problem over a short period of time. Bloch decided to investigate. By asking the right questions, he found that all of the boys had used over-the-counter products containing lavender oil or tea tree oil on their hair or skin.

He then involved researchers Derek Henley and Kenneth Korach of the National Institute of Environmental Health Sciences, who tested the oils on human breast cells. Both oils acted like the female hormone estrogen. The oils also decreased male hormone response.

When the boys stopped using the products, the problems resolved.

Many consumers are exposed to lavender and tea tree oil in personal care and cleaning products, including bath oils, shampoos, soaps, laundry detergents and skin lotions.

"There's definitely an association between exposure to lavender oil and tea tree oil and gynecomastia [abnormally large breasts in men]," said Derek Henley, lead author of the research and a postdoctoral fellow at the National Institute of Environmental Health Sciences, in Research Triangle Park, N.C

There are many environmental sources which mimic estrogen, including ingredients in plastics and hormones in meat. They are all of concern because of their potential link to immune responses, cancer and other serious health problems. This finding is the first to implicate "essential oils" from plants as estrogen mimics.