I think it's because of the finger paint... Also certain types of hairsprays can make the paint chip, got2b by Schwarzkopf is one of those... it's great for styling wigs but it's not something you want to use for fixing bodypaint.
[link] <-- That's all I use. I own several of those, but you don't need more than one and it lasts pretty long considering how small it looks (I still haven't ran out of the one I bought last September)