Erythema on the body should consider a variety of conditions: First, urticaria, whose lesions are characterized by edematous erythema as well as wind clusters, round, oval or irregular in shape, can be isolated or fused into patches, with an uneven surface and an orange peel-like appearance, the erythema can fade on its own, leaving no traces, and the fading time does not exceed 24 hours, and can recur. Oral antihistamines can be chosen for treatment, such as loratadine and cetirizine are common. Second, common psoriasis, its initial lesions are red papules or macules, gradually forming red plaques, covered with thick silvery white scales, lesions can occur in all parts of the body, often symmetrically distributed. Topical vitamin D3 derivatives, such as carbofurantrin and tacalcitol, and calcium phosphatase immunosuppressants, such as tacrolimus, are available.