Alum, also known as wrought alum and alum, is soluble in water or glycerin and insoluble in alcohol. The aqueous solution of alum exhibits the properties of aluminum, potassium and sulfate salts. The main component of alum is aluminum potassium sulfate dodecahydrate, which can not be discharged from the body after entering the body, and it will be deposited in the body forever. Alum has anti-inflammatory, dampness, antidiarrheal, hemostatic, detoxification, insecticidal and other effects and functions, dermatology commonly used alum treatment of yellow sores, scabies, fungal infectious skin diseases, and insect bite dermatitis, burns, scalds and other skin diseases. Alum can sometimes be used externally as an astringent, soaking hands and feet to treat sweaty hands and feet.