alum stick/block(Shaving/deodorant Alum Block )/stone (natural)(personal care) Alum is a natural antiseptic that, when used for shaving, can calm irritated skin and stop bleeding on any cuts. To use, you simply get it wet and rub it over your skin, pausing for a few seconds on any cuts. Given that it is an astringent, it will sting a bit. Alum is actually a salt and was first used for shaving 4000 years ago by the Egyptians. This type of alum, potassium alum, can also be used as a natural deodorant often referred to as "crystal deodorant