Scales are thin flakes of epidermal keratin layer that are about to be shed or have been shed. Its size, form, thickness, quantity and color vary, some are dry, some are greasy; most of them are secondary damages of skin diseases with erythema or papule damage (such as psoriasis, seborrheic dermatitis, pityriasis rosea). Diagnostic examination I. Ask for medical history. II. Physical examination. Observe the occurrence site, size, number, degree of edge regularity and color of scales. Third, laboratory tests. Exclude connective tissue disease, etc. Take scales pathological examination. V. Pathogenetic examination. Find bacteria, virus, fungus, spirochete, etc.