craftgrrl | One other question on bath bombs

I've seen in a lot of recipes that Borax is used.

What's the actual purpose of it in the recipe? Is it used as a stabilizer? to prevent growth of bacteria? (it *IS* a pesticide, afterall) or what? It just seems a bit toxic to be putting in your bath unless it's crucial for some reason. Anyone know?

Thanks for all the help, I really appreciate it!! I've been lurking here for ages and suddenly find myself chock-full of questions :-P