Frequent exposure to lavender or tea tree oil may be linked to prepubertal gynecomastia in young boys, according to study data presented at ENDO 2018: The Endocrine Society Annual Meeting, held March 17-20 in Chicago, Illinois

To investigate the potential association between male gynecomastia and essential oils, study authors from the National Institute of Environmental Health Sciences (NIEHS) analyzed 8 common components included in lavender and tea tree oils.

Four of the chemicals (eucalyptol, 4-terpineol, dipentene/limonene and alpha-terpineol) were present in both lavender and tea tree oils whereas the others (linalyl acetate, linalool, alpha-terpinene and gamma-terpinene) were found in either oil.

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After testing these against human cancer cells, researchers found all 8 chemicals had varying estrogenic and/or anti-androgenic properties. These changes were consistent with endogenous hormonal conditions that trigger gynecomastia in prepubescent boys.

“Our society deems essential oils as safe,” said study lead investigator J. Tyler Ramsey, a postbaccalaureate research fellow at the NIEHS, part of the National Institutes of Health. “However, they possess a diverse amount of chemicals and should be used with caution because some of these chemicals are potential endocrine disruptors.” The researchers added that many of the chemicals they tested are also found in at least 65 other essentials oils. 

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Ramsey JT, Li Y, Arao Y, Korach K. Steroid receptor hormonal actions of lavender and tea tree oil components. Presented at: ENDO 2018: The Endocrine Society Annual Meeting; Chicago, IL; March 17-20, 2018. Abstract OR22-6.

This article originally appeared on MPR