I use benzoyl peroxide on a regular basis to prevent mild acne, and when I became pregnant I researched it because it is really the only thing that works for me. There isn't a whole lot of data for its use during pregnancy, but what I have read suggests that the small concentration (2.5%) used topically is absorbed in such small amounts, and then broken down by the body, that it is highly unlikely to have a negative effect on the fetus. I know it's not entirely free from risk, due to lack of research proving it to be such, but I choose to take what I consider to be a small risk. With my DD i stopped using it for the first few months and had such bad acne that I was borderline depressed.
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