There’s long been an unwritten rule that pregnant women shouldn’t dye their hair, for fear of causing undue harm to the fetus growing inside of them. It’s unclear what sparked this concern, but women continue to ask: Is it safe to dye my hair while pregnant?

Women’s worries about hair dye chemicals, such as ammonia and peroxide, are understandable. But as StyleCaster reported, the concentration of chemicals in hair dye is very low. Are the small quantities used to color your hair enough to put you at risk for serious health problems?