Erythema is a type of maculopapular rash, which is a reddish lesion on the mucous membranes of the skin, with the height of the lesion being flush with the surrounding skin. Causes of erythema include lupus erythematosus and urticaria. 1. Lupus erythematosus: it is a chronic and recurrent autoimmune disease caused by autoimmune abnormality, the most characteristic clinical manifestation is facial butterfly-shaped erythema, and there can be many kinds of erythema such as discoid erythema, frostbite-like erythema and so on. Generally, SLE is mainly treated by glucocorticoid combined with immunosuppressants, such as prednisolone and hydroxychloroquine. 2. Urticaria: It is caused by drugs or other factors to increase the permeability of small blood vessels in the skin and mucous membranes, resulting in localized edema as well as red lump-like elevations of varying sizes on the skin. The treatment of urticaria is mainly to remove the cause of the disease, available second-generation non-sedating antihistamines such as loratadine to control symptoms, if the treatment is ineffective, available glucocorticosteroids such as prednisone. In the use of drug therapy should be under the guidance of a doctor. When patients appear erythema, should immediately go to the hospital, follow the doctor’s instructions for treatment, do not self-medication.