Purpura is a bleeding disorder, the common purpura in clinical practice are allergic purpura and immune thrombocytopenic purpura, both of which can recur. The precursor of recurrence of allergic purpura is that the patient has bloating, nausea, even vomiting blood, black stool without any obvious reason, and sometimes joint swelling and pain, and these symptoms are likely to be recurrence of allergic purpura. Immune thrombocytopenic purpura, the symptoms of relapse are unexplained bleeding spots and petechiae on the skin and mucous membrane, sometimes bleeding from the nose and gums, increased menstrual flow in women, serious bleeding from internal organs, etc. This situation indicates that the immune thrombocytopenic purpura is about to relapse, if the blood test, the platelet count is likely to drop to a very low level.