Few studies have examined the effects of hair dyes on the developing human fetus. Therefore, it isn’t known if there is any real risk. When chemicals are applied to the scalp, says Marjorie Greenfield, MD, associate professor of obstetrics and gynecology at University Hospitals, Case School of Medicine in Cleveland, small amounts will get into the bloodstream, but “most chemicals are cleared from your bloodstream fairly quickly.”

Jason Rubin, MD, tells Real Health, “It’s unlikely that hair coloring would harm the unborn child because of the short amount of time the chemicals are in contact with the skin. There’s a higher risk of absorption and fetal exposure with daily use products, such as moisturizers, sun screens and skin creams.

“Pregnant women should always be cautious when deciding which chemicals they put on their skin,” Rubin continues. “Small amounts of topical ingredients you use each day are absorbed into your bloodstream. From there, they can easily pass into the developing baby’s circulation [system]. Some commonly used ingredients have links to birth defects and some don’t, but most have never been studied so the risk is unknown.”

Doctors recommend waiting until after the first trimester to use hair color to ensure that a baby’s organs are formed before using anything that might pose a risk. Dr. Greenfield feels these recommendations have more to do with whether a doctor is a worrier (“better to just avoid possible exposure”) or not (“no evidence of risk, so don’t worry”) than actual safety data. A more balanced view is to do research, collect information and consult with your obstetrician. “Without researching each ingredient, you can never say that a topical product is completely safe to use during pregnancy,” Rubin says. “Expecting mothers must choose for themselves how careful they want to be.”