The redness of the skin when scratching may be related to physiological factors such as excessive force, or it may be caused by artificial urticaria. 1. Physiological factors: the redness of the skin when scratching is considered to be caused by a greater force, excessive force when scratching the skin, which is a normal situation and will not be accompanied by other symptoms. 2. Artificial urticaria: the cause of the disease may be related to friction, scratching and other factors, contact with hot water, exercise, cold and other reasons may also trigger the disease, the patient in the scratching, scratching the skin after the localization of the line will appear to bulge the wind, surrounded by a red halo, may appear itchy. If the skin appears to be red when scratching, after excluding physiological factors, it is recommended that the patient go to a regular hospital to consult a doctor for examination, to clarify the cause of the disease and then symptomatic treatment.