Recently, the news reported that lavender and tea tree oil may cause gynecomastia (breast growth) in young boys.
The underlying study described three young boys. One was exposed to lavender essential oil in a “compounded healing balm” “starting shortly before the visit to the doctor for gynecomastia. The condition resolved within 4 months of discontinuing use of the balm. The second boy used a styling gel on his hair and scalp every morning and regularly used a shampoo. Both the gel & the shampoo listed lavender oil and tea tree oil as ingredients. Nine months after discontinuing use, his gynecomastia was substantially reduced but still present. The third used a “lavender-scented soap” and intermittently a lavender-scented skin lotion. His gynecomastia resolved completely after discontinuing the products. His fraternal twin brother used the lotion but not the soap without any problems.
Based on the researchers’ in vitro studies showing that lavender oil and tea tree oil “possess weak estrogenic and antiandrogenic activities” they “suspect” that these essential oils caused these cases of gynecomastia.
The problems with the study are obvious: There is no convincing correlation between the products and the resolution of gynecomastia, and a rechallenge was not done. The study completely ignored the other ingredients in the various products used. Many body care products, for instance, contain parabens that are strongly estrogenic. And some of the products may not have contained either lavender or tea tree oil. “Lavender scent” usually refers to a synthetic compound, not lavender oil. The news this little “study” generated shows a disturbing bias against natural products.
Henley DV, Lipson N, Korach KS, Bloch CA. Prepubertal gynecomastia linked to lavender and tea tree oils. New England Journal of Medicine 2007; 356:479-485.