Most cases of male prepubertal gynecomastia are classified as idiopathic. We investigated
possible causes of gynecomastia in three prepubertal boys who were otherwise
healthy and had normal serum concentrations of endogenous steroids. In all
three boys, gynecomastia coincided with the topical application of products that
contained lavender and tea tree oils. Gynecomastia resolved in each patient shortly
after the use of products containing these oils was discontinued. Furthermore,
studies in human cell lines indicated that the two oils had estrogenic and antiandrogenic
activities. We conclude that repeated topical exposure to lavender and tea
tree oils probably caused prepubertal gynecomastia in these boys