Wait a minute before dabbing lavender essential oil on your male child: A new study finds that regular exposure to certain plant-derived oils puts boys at risk of prepubertal gynecomastia—or, as Science Alert bluntly puts it, "man boobs." "Our society deems essential oils as safe," says the developmental biologist who led the study. "However, they possess a diverse amount of chemicals and should be used with caution because some of these chemicals are potential endocrine disruptors." That essentially means they can mess with hormones, and there have been a number of cases of young boys developing breasts after topical exposure to lavender and tea tree essential oils, per a press release. (In those cases, symptoms subsided after exposure was halted.) The new study analyzed eight common chemicals out of the hundreds found in those two oils.
Scientists tested the chemicals against human breast cancer cells and found that all eight of them were indeed endocrine disruptor chemicals (EDCs) and displayed levels of estrogen-like properties and/or testosterone-inhibiting properties—meaning they could play a part in stimulating mammary gland conditions in a prepubescent male body. And many of those chemicals are also in at least 65 other essential oils, the lead author says, which is particularly concerning since the FDA does not regulate essential oils and no prescription is required to buy them. They're currently popular for use in everything from cleaning products to toiletries to alternative health treatments. The study authors say essential oils should be used with caution, but Science Alert notes that there is, so far, limited research on these effects and the latest findings have not yet been peer-reviewed. (The fervor for essential oils is bad news for frankincense forests.)