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 their armpits.

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).