Generally speaking, alum is mainly used in chemistry. The most well-known function of alum is as a water purifier, which is used to precipitate impurities in water and purify water. In addition, alum actually has astringent effect, which can inhibit excessive sweating of the skin and prevent bleeding from small wounds. It can also be used as a resist to make the pattern outline of cloth clear and the color stable.

Alum is a kind of food additive, which is most commonly used in making fried dough sticks. Alum is also used as a leavening agent to help the fried dough sticks expand and make them brittle, especially on the surface of the fried dough sticks. Fried dough sticks with alum are not easy to soften, and their appearance looks more beautiful after cooking.