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Emily Oster

2 minute read Emily Oster

Emily Oster

Is Hair Dye Dangerous During Pregnancy?

Q&A on chemicals

Emily Oster

2 minute read

Is hair dye safe in pregnancy? If so, better in one trimester than another?

—Going White Fast!

The primary concern with hair dye is that toxic chemicals in the dye will affect the baby. In very high doses, some of the chemical components of hair dye can increase birth defects in rodents. They can also cause cancer (again, in rats). This is a concern in principle, of course, but it is something of a stretch to compare the impact of directly injecting the pregnant rat with high doses of chemicals every day during pregnancy to three or four incidents of topical exposure (which is what you get from actually dyeing your hair).

Human studies have generally not shown any association with an increased risk of birth defects. A couple of small studies have suggested a link with childhood cancer later, although larger studies have not confirmed this. Overall, the rat evidence doesn’t seem to translate to a human link.

hair dye in Pregnancy
Nataliya Vaitkevich / Pexels

In addition to birth defects and cancer, one study comparing hairdressers in Sweden with the rest of the Swedish population showed a small but statistically significant increase in low-birth-weight babies among the hairdressers. Because hairdressers work with hair dye more than the average person, this finding led to the concern that perhaps at high doses hair dye affects birth weight. In the end, this finding wasn’t supported by other studies, and it seems likely that the result was driven by other aspects of the job (for example, the fact that hairdressers spend much of their time standing up).

There are a number of detailed reviews of this issue, and they all argue pretty compellingly that there is no reason to worry about hair dye use anytime in pregnancy. In fact, even the American College of Obstetricians and Gynecologists suggests it’s fine after the first trimester. To be fair, you should probably avoid injecting yourself with hair dye during the first trimester (or really at any time). Getting rid of a few gray hairs or touching up your roots is a different story.

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