Alum refers to a chemical compound whose name is often given as potassium aluminum sulfate. It is a crystalline substance that can be colorless or white.
Filipinos use tawas in doing laundry and in whitening armpits. It is now available scented and in powder form.
Tawas is also used by Filipino folk healers to make a sign of the cross on the forehead of a person thought to be the victim of a mangkukulam (witch) or duwende (dwarf).