Alum can be used topically mainly to kill insects, stop sweating, stop itching, stop bleeding and promote healing, and is often used in the treatment of skin diseases, such as eczema, and can also reduce foot sweating and prevent foot odor. 1, kill insects: alum topical can help kill a variety of parasites such as scabies and mites, and can also inhibit the growth of pathogenic bacteria such as fungi, and is effective for fungal infections of the feet or vulva. 2, stop sweating. For sweat secretion is more, palms or feet are prone to sweating, external use of alum solution or alum solution, can also inhibit the secretion of sweat glands, thus reducing the case of odorous sweating. For eczema, if the exudation is more obvious, topical alum solution can stop the exudation and let the skin tend to dry or restore the normal appearance; 3, stop itching: alum solution or powder used on the skin surface can usually help control itching and make the skin less sensitive to external stimuli; 4, stop bleeding: for blood in the stool in the perianal or vulva area, or bleeding caused by hemorrhoids, and superficial skin ulcers caused by Bleeding, external application of alum solution or other preparations, has a better hemostatic effect; 5, promote healing: for ulcers that are difficult to heal, the external application of alum can shorten the time of wound healing. In addition, external application of alum to burn wounds can also play a better role in promoting wound healing. Although alum has certain benefits when applied topically, it should not be used indiscriminately and a doctor needs to be consulted before use to avoid allergic and other adverse reactions.