What’s really in hair dye, and is it safe to use? Some research on hair dye safety dates back decades, so one might assume it’s out of date; however, the main ingredients are unchanged. Younger women are particularly vulnerable to harm from exposure to chemicals in hair dye that mimic or block estrogen.
This comprehensive and balanced article at webmd.com provides links to research on the topic of risk from hair dyes. It also includes a link to an on-line tool with data on specific personal care products.