Skin with a coin-sized circle of red color may be coin-shaped eczema, copper ringworm. 1. Coin-shaped eczema: coin-shaped eczema belongs to a special type of eczema, the skin lesions are round or round-like, such as the shape of a coin. Usually appearing on the limbs, the main symptom is that the red rash gathers to form round plaques and is accompanied by itching. As the disease progresses, the number of round lesions may gradually increase and papules or blisters may appear. Pay attention to daily skin hygiene, avoid scratching with hands, and avoid using alkaline substances, such as soap and detergent. 2. Ringworm: Ringworm is a fungal infection, the pathogen is red trichophyton. The manifestation is a coin-sized round or ring-shaped erythema with blisters on the edge, similar to copper coins. The lesions are mainly pimples, papules, blisters and red plaques covered with scales that are well demarcated from the surrounding normal skin and conscious itching. It can be treated with medications under a doctor’s supervision, such as external application of tretinoin econazole cream, terbinafine hydrochloride gel or bifonazole cream. The appearance of a coin-sized circle of red skin is recommended to go to the hospital in a timely manner, after clarifying the cause of the disease under the guidance of the doctor symptomatic treatment. In daily life, drink more water, rest more, avoid overwork.