Are hair relaxers unsafe during pregnancy?

Probably. I have historically counseled all my pregnant patients to avoid all extraneous "products"/"chemicals" during their pregnancy. Even though hair relaxers are applied topically; they are absorbed through your scalp and the make-up of the products is the unknown. Some might argue differently but I always err on the side of caution; better to avoid in the short term than risk long term problems.
Hair relaxer pregnan. I would not suggest using hair relaxers when you're pregnant. The sulfur can be problematic and you don't want to risk anything to your baby when you're pregnant.