The inexplicable red marks on the body are considered as follows: 1. Pressure purpura: It is caused by tight belt, crying or overexertion, resulting in increased permeability of superficial skin capillaries and extravasation of red blood cells. 2. Urticaria: It may be caused by allergic factors, cold stimulation factors, strenuous exercise, severe infection or internal diseases. In clinical treatment, anti-allergic treatment is needed, oral olopatadine hydrochloride tablets, topical glycolic lotion. 3, erythema multiforme: may be due to allergic factors or viral, bacterial, fungal infections and the resulting irritation reaction.