Allergic purpura rash is getting more and more, it may be related to the failure to get rid of the causative factors, such as the infection foci still exists as well as continue to take the suspicious drugs or food, malignant tumors can also cause allergic purpura. Allergic purpura may be associated with infections (bacteria, viruses), drugs, food, malignant tumors and other factors, causing allergic vasculitis, manifested as a predominantly symmetrical purplish-red papules and purpura on the extensor side of the calf, which may be accompanied by abdominal pain, renal damage, arthritis and other symptoms. We should actively search for the causative factors, prevent infection, avoid taking suspicious drugs and food. Most of the allergic purpura is self-limiting, if the patient’s allergic purpura rash is getting more and more, and also need to be identified with idiopathic thrombocytopenic purpura and so on. It is recommended to go to the hospital in time to avoid delaying the condition.