They may cause cancer. The Medical Detective asked experts, “Should she, or shouldn’t she?” Read on to learn the truth about coloring hair, where the harshest chemicals lurk and how to tone down gray the healthy way…Many women would rather face a root canal without Novocain than let their locks go gray. “It’s important for my self-esteem,” says Gaynell Warcola, a 60-year-old Los Angeles social worker who’s been covering her gray for years. Her stylist touches up her brunette coif every 5-6 weeks. “I don’t want to look like a skunk,” she says. Nor do most women, who brave the possibility of cancer by frequently coloring their hair. So, is all that dyeing… to die for?

Para-phenylenediamine (PPD) creates dramatic color changes – going from blond to brunette, for example – but has caused cancer in animals, according to the Food and Drug Administration (FDA), which regulates some hair dyes. Women worried about hair dye’s cancer risk should “decrease their frequency of permanent hair dye use or use non-chemical-based or natural hair dye [without PPD],” advises Manuela Gago-Dominguez, M.D., Ph.D., assistant professor at the Keck School of Medicine and USC/Norris Comprehensive Cancer Center in Los Angeles.Coal tar is a combination of chemicals that create longer-lasting colors than natural, vegetable dyes. It also caused cancer in laboratory animals, according to the FDA. Because of that, products with coal tar must include a warning saying some people may experience skin sensitivity; users should perform a skin test before use; they should follow instructions provided; and the product must not be used for dyeing eyelashes or eyebrows – to do so may cause blindness.

Keep the mixture on your hair only as long as recommended on the box, says veteran colorist Sheri Caroll at George Caroll Salon in Los Angeles.Wear gloves when applying the mixture. Some chemicals are toxic, so minimize exposure.Try to keep the color off your scalp, a pathway to internal chemical exposure. Skin exposure also raises your risk of an allergic reaction. Applying with a brush or comb may help keep dye from your scalp.Don’t combine different hair dye products; they may have harmful reactions.Rinse your scalp thoroughly with water after dyeing.