The cause of allergic purpura is not yet clear, and may be caused by infection, drugs, genetics and other factors. Allergic purpura is a common vascular allergic reaction disease, in which the body has an allergic reaction to certain sensitizing substances, leading to an increase in capillary fragility and permeability, and causing inflammation and hemorrhage in small blood vessels of the skin, joints, intestines, and kidneys. Since the etiology and pathogenesis of allergic purpura have not been clearly defined, it may involve infections with pathogens such as bacteria, viruses and parasites. Or it may be caused by the use of antibiotic drugs, such as penicillin and cephalosporins, or by the use of antipyretic and analgesic drugs, such as salicylates and indomethacin, among other factors. There is a certain genetic component to the disease, and it can also be caused by stimulation from external factors, such as pollen, mosquito bites, and cold air stimulation. If allergic purpura is suspected, patients are advised to go to regular hospitals and undergo relevant examinations to determine the cause of the disease. Once diagnosed, the patient should actively cooperate with the doctor to take relevant treatment measures to avoid delaying the condition.