Allergic purpura, also known as hemorrhagic capillary poisoning, is a relatively common microvascular allergic hemorrhagic disease. It is a systemic vascular disease that is due to an allergic reaction of small arteries and capillaries to certain substances. The basic lesion is an extensive aseptic inflammatory reaction of capillaries and small arteries, causing increased permeability of the vessel wall and exudative hemorrhage and edema. The most common clinical symptoms are skin purpura, which can be accompanied by symptoms of gastrointestinal tract, joints and kidneys, so clinically, allergic purpura is divided into simple skin type, joint type, abdominal type, allergic purpura combined with nephritis type and mixed type.