If the red spots on the calf area appear painless and itchy, it is necessary to carefully observe the appearance of the small red spots in order to determine how the factors are formed. If the erythema has no obvious color fading after pressing with hands, it is considered that it may be purpuric disease, which is due to the increase in the fragility of subcutaneous capillaries, resulting in the accumulation of blood in the subcutaneous after the formation of a clinical appearance, and the situation is divided into allergic purpura and thrombocytopenic purpura, allergic purpura has mild itching, and no pain and no itching is considered to be thrombocytopenic purpura, which needs to go to the hematology department for treatment. The condition needs to go to the hematology department for treatment. If the erythema growing on the legs has faded after pressing, and soon returns to the appearance of erythema, it is considered that it may be persistent erythema, which may be secondary to eczema, dermatitis, folliculitis, and can be treated with mucopolysaccharides polysulphate cream externally.