Recent media comments about lavender and tea tree oils causing breast growth in young boys (prebubertal gynecomastia) have grossly exaggerated the risks. Three cases (all, curiously, in Denver, Colorado) are cited in the New England Journal of Medicine which young boys experienced enlarged breast tissue, and all were allegedly using products containing lavender oil. One was allegedly also exposed to tea tree oil. However, the researchers to ascertain whether they did in fact contain lavender or tea tree oil analyzed none of the products. Even if they did, we do not know whether they contained sufficient quantities to have a physiological effect. Derek Henley, who authored the research on which these reports are based, has said there is "not enough evidence to suggest people should stop using products containing these essential oils, even young boys", and that no firm conclusions can be drawn.

The details given about the cases are sketchy, but there is good reason to believe that tea tree oil could not have had any effect at all and that, in another case, lavender oil could not have caused gynecomastia. Further, the researchers failed to check for chemical hormone disruptors, such as parabens, pesticides and phthalates, which may have been in the products concerned. Laboratory testing did show evidence that both essential oils had an estrogen-like action, and this had not been previously reported. However, it cannot be assumed that the same will happen in humans. Any correlation between the laboratory testing and the three cases in question is at best circumstantial. Prepubertal gynecomastia is an extremely rare condition. Both lavender and tea tree oil are present in aromatherapy cosmetics used by millions of people, who should be assured that they can continue to use them safely.