Purple ecchymosis appearing on the body for no reason may be caused by trauma or due to hematologic diseases such as immune thrombocytopenic purpura and leukemia. 1. Trauma: Purple ecchymosis can be produced on the skin due to capillary rupture and bleeding after local tissues are traumatized. 2. Immune thrombocytopenic purpura: it is an autoimmune disease in which autoantibodies in the blood destroy platelets and megakaryocytes, leading to a decrease in platelets in the blood, which can lead to ecchymosis and petechiae in the skin and mucous membranes. 3. Leukemia: it is a malignant tumor of the hematopoietic system, which will inhibit the bone marrow and other hematopoietic tissues leading to hematopoietic dysfunction, and the platelets will be reduced accordingly, and there will be symptoms such as bleeding and ecchymosis of the skin and mucous membranes. Purple petechiae appear on the body for no reason should be timely to the hospital, improve the relevant examination to clarify the cause of the disease, under the guidance of the doctor symptomatic treatment.