Alum (potassium aluminum sulfate) is a food additive that is ideal for pickling and canning. It helps create crisp pickled fruits or vegetables.
Alum, a naturally occurring ingredient is considered to be good for tightening the skin. It has an astringent property that causes the cells to shrink and removes excess oil from the skin. Thus, Alum is used in the form of gels or creams for skin care