I was reading an article lately and it pointed out that the main active ingredient in antiperspirants is aluminum zirconium tetrachlorhydex. that means that every time you put it on, you are giving yourself a hearty dose of aluminum, which has been proven to be related to alzheimer's and other medical problems. i dont know about you, but i'm giving up antiperspirants and sticking to plain deodorant.
Mind you, there's a small section on Wikipedia regarding this. Now before you bash the heck out of me for even mentioning Wikipedia, it's just a few bad apples giving it a bad name. The site's decent enough, and a majority of the users tend to cite information they print. So, it's not all that unreliable.