Hair dye, I agree, is some pretty scary stuff.
Nair, on the other hand, is probably one of the more harmless (from a toxicity perspective) things in the bathroom.
The active ingredients are just calcium and sodium hydroxide, which are strongly alkaline and break up the chemical structure of the hair. That's not to say the product is harmless in general, you can still burn yourself quite badly with it (think the lye on the hand scene in Fight Club - same active ingredient!), but it's not toxic. NaOh and CaOh are too reactive to get absorbed into your system, they'll just react with the oils in your skin to make soap!