I did a lot of research on this, because I used to dye my hair and worked in a salon so was going to be surrounded by it regardless. The truth is that while "they" advise against it- there's been no substantial evidence that it's actually harmful. The theory is that it's not good to be breathing in those chemicals and if you're using bleach on your scalp, that can sometimes not be good. But basically it's okay, I dyed my hair while pregnant (but used amonia free dye) and everything was fine. I'm not sure if you do it professionally or not, but if you do it yourself- it's best to buy hair dye at a beauty store, because those boxes at the grocery store actually contain a lot of bad/harsh chemicals that aren't good for your hair in general.
at 9:14 PM on Jan. 20, 2011