Hives, or urticaria, a sudden attack of red bumps and wheals on the skin, typically last up to one day, according to WebMD. The itchy swollen bumps can strike anywhere on the body, including the face and mouth. Angioedema, a variation of hives, is marked by swelling under the skin.
Other types of hives include acute urticaria, which lasts up to six weeks; chronic urticaria, lasting longer than six weeks; physical urticaria; and dermatographism. Hives result from blood plasma leaking out of blood vessels in the skin, according to WebMD. This leakage is a reaction to histamine, a chemical released from cells located along blood vessels of the skin. Histamine may be released due to allergic reactions, food-borne chemicals, insect stings, sunlight or some medications. However, sometimes the exact reason for hives is unknown.