There are many reasons for the appearance of painless red patches on the skin, such as purpura, hemangioma, lupus erythematosus, and urticarial vasculitis. 1. Purpura: Purpura is mainly caused by bleeding and exudation of capillary rupture, usually not accompanied by uncomfortable symptoms, the skin can show purplish-red, red petechiae ecchymosis, and does not fade when pressed. 2. Hemangioma: red patches of skin that do not hurt or itch may also belong to hemangioma, the area can follow the age and gradually expand, most of them can fade after pressing, and will not be accompanied by pain or itching. 3. Lupus erythematosus: Lupus erythematosus can also be manifested in the appearance of raised red patches on the skin, and most of the cases will not be accompanied by pain or itching. 4. Urticaria vasculitis: Urticaria vasculitis is an autoimmune disease, which can also be characterized by the appearance of painless red patches on the skin. There are many reasons for the appearance of itchy red patches on the skin, and after the appearance of the phenomenon, it is necessary to consult a doctor for a clear diagnosis, and then take standardized treatment under the guidance of the doctor.