Just thought I'd chime in here as I use my "alum" as both an aftershave and a deodorant.

I buy the Crystalux brand and they used to have a very interesting and informative website so of course it is now under re-construction.

What I remember from their site is that alum blocks do not contain Aluminum, ie. do not cause alzhiemers.

They are also not an anti-perspirant (believe me this I can attest to). But control oder by destroying the bacteria that cause it. They do work quite well as a deodorant. You do have to get used to the fact that there is no scent, not even as much as a non-scented stick. I am alergic to the common aluminum salts used in most deodorants (hives and such) but have no reaction to these.