Purpura is a group of clinical syndromes characterized by extensive skin mucosal bleeding due to dysfunction of capillaries, platelets, and clotting factors. The common purpura diseases in the clinic are allergic purpura, immune thrombocytopenic purpura and hemophilia, etc. Allergic purpura is a capillary hemorrhagic inflammation of the whole body caused by allergy to infections and external factors, manifesting as symmetrical purpura of the extremities, which can appear repeatedly in batches. Immune thrombocytopenic purpura is a widespread hemorrhage of the skin and mucous membranes throughout the body due to the production of autoantibodies against platelets, resulting in excessive destruction and reduction in the number of platelets. Hemophilic purpura is a purpura of the skin caused by the lack of coagulation factor VIII or coagulation factor IX and coagulation dysfunction.