Is hair dye safe in the first trimester?

What does the evidence say about hair dye in the first trimester during pregnancy?

1. Under normal conditions, the amount of hair dye absorbed by healthy scalp skin is small, and absorption depends on factors like skin condition, ingredient concentration, how much area is covered, and how often it's used. 1
2. Allergic reactions to para-phenylenediamine (PPD), the ingredient in permanent hair dye most associated with skin sensitization, affect a meaningful minority of people (patch-test positive rates around 4 to 6 percent by region) but reflect an allergy risk rather than a pregnancy-specific one, and wearing gloves during application is the standard way to reduce contact for anyone using dye, pregnant or not. 2
3. Based on the studies MotherToBaby reviewed, getting or performing hair coloring is not expected to significantly increase the chance for birth defects when used correctly, and animal research hasn't shown an increased miscarriage risk either; the fact sheet does flag formaldehyde-releasing hair-straightening products as a specific caveat, a different product category from standard dye. 1
4. MotherToBaby's hair-product reference list compiles the underlying research on hair dye and reproductive outcomes, including studies of hairdressers and cosmetologists specifically, without stating any first-trimester-specific restriction or 12-week waiting period. 3
5. A review of occupational chemical exposure among hairdressers notes that reproductive effects have been studied because hairdressers are predominantly women of childbearing age, but this research is about all-day, repeated occupational inhalation exposure in a salon, a different category from someone dyeing their own hair once every several weeks at home. 4

Is hair dye in the first trimester safe in each trimester?

• First trimester. There's no evidence-based restriction specific to this trimester. If waiting still feels more comfortable to you personally, that's a reasonable choice too, just not one the research requires.
• Second trimester. Same guidance continues. Absorption through healthy scalp skin is small under normal conditions, and techniques like highlights, which don't touch the scalp, involve even less contact.
• Third trimester. Same guidance continues, with formaldehyde-releasing hair-smoothing products (a different category from standard dye) worth avoiding specifically, per the same fact sheet's caveat.