The body itchy scratch on the red piece may be idiopathic thrombocytopenic purpura, eczema and urticaria and other causes. 1. Idiopathic thrombocytopenic purpura: Usually the patient’s own blood platelet antibodies exist in the blood, destroying the normal platelets in the body, which will lead to their own bleeding symptoms. After scratching the itchy skin, the skin and mucous membrane will bleed, forming pinpoint red or purple spots. 2. Eczema: usually patients with skin allergies or long-term skin moisture may lead to eczema, eczema may lead to local itching and discomfort, the patient will scratch the phenomenon of congestion and swelling, resulting in the formation of red spots. 3. Urticaria: Urticaria is due to increased vascular permeability resulting in limited edema of the skin mucous membranes, usually the patient will cause itching after scratching, resulting in the formation of erythema. The body itchy scratch a red piece of may have other reasons, it is recommended that patients actively seek medical attention, clear cause of the disease under the guidance of the doctor for standardized treatment.