Allergic purpura is a hemorrhagic disease of vascular metaplasia, also called immune vascular disease. The pathogenesis is mainly the body’s metamorphic reaction to certain substances, causing increased capillary permeability and fragility, and accompanied by small vessel inflammation. The clinical manifestations are: skin purpura, mucosal bleeding, arthritis, abdominal pain, nephritis, etc., but the laboratory test results are not abnormal findings. Allergic purpura is caused by multiple etiologies: 1, bacteria and viruses 2, parasitic infections 3, food 4, drugs 5, other causative factors: cold, pollen, tuberculin experiments, and even psychiatric factors can cause the disease.