Q. Do hair dyes cause cancer?
The scientific evidence to date is inconsistent and thus inconclusive regarding cancer risk in people who regularly dye their hair. Some observational studies have shown links to a slightly increased risk of lymphoma, for instance, and to breast cancer, but others have not. Most recently, a study in BMJ in 2020 that used data from 117,200 (mostly white) women did not find an association between permanent hair dye and most cancers or cancer mortality, though it did link the dyes to basal cell carcinoma and some breast cancers and ovarian cancer.
Moreover, the research is difficult to interpret, since hair dyes contain so many different ingredients, products vary, and formulas have changed over the years. Some chemicals, including aromatic amines—which were found to cause cancer in lab animals—were removed several decades ago, so the risk may be different today than in the past. Even the evidence in hairdressers, who have higher long-term exposure, is equivocal.
The International Agency for Research on Cancer (part of the World Health Organization) has said that because of inadequate evidence, it could not classify personal hair dyes—as opposed to occupational exposure—in terms of its carcinogenicity risk to humans. In contrast, the government’s National Toxicology Program has classified some chemicals found in hair dyes as “reasonably anticipated to be human carcinogens.” Clearly, more research is needed, particularly regarding occupational exposure in hairdressers.
If you’re concerned about safety, leave the product on for the shortest time possible, rinse thoroughly, and use in a well-ventilated area. You might also try henna or other non-permanent plant-based dyes, though these don’t cover gray as well and fade sooner.
