Sudden bruises and purple patches on the body are considered to be related to trauma, purpura, aplastic anemia, and disseminated intravascular coagulation. 1. Trauma: mainly reflected in the body parts suffered from external objects after the blow, collision, usually the body suddenly green and purple phenomenon can be disappeared with the passage of time. 2. Anaphylactic purpura: the cause of the disease is not clear, may be related to infection, immune disorders and other factors. Typical symptoms of patients include skin purpura, joint swelling, abdominal pain, blood and protein in urine, etc. It can also be manifested as purple ecchymosis and petechiae on the body. 3. Aplastic anemia: the disease is related to congenital genetic factors, viral infections, immune disorders, etc. Patients will have bleeding spots on the skin, which are easily accompanied by weakness, dizziness, palpitations, shortness of breath and other discomforts, and can also be manifested as a sudden bruise or purple bruise on the body. 4. Disseminated intravascular coagulation: the disease can also cause some patients to have sudden bruises and purple patches. The disease is related to serious infections, malignant tumors, etc., and the patients will have spontaneous bleeding, shock, and microthrombosis. In addition, excessive skin elasticity, sepsis, vitamin C deficiency, hemophilia, etc. can also cause sudden bruising and purple patch, and patients are advised to seek timely medical treatment.