Scales are thin flakes of epidermal keratin layer that are about to be shed or have been shed. Its size, shape, thickness, quantity and color vary, some are dry, some are greasy; most of them are secondary damages of skin diseases with erythematous or papular damages (such as psoriasis, seborrheic dermatitis, pityriasis rosea). Diffuse redness and swelling of face, hands and feet or whole body, swelling subsides in about 3 weeks, branched or leaf-like flaking begins to appear, hands and feet are broken gloves or broken sock-like shedding, hair and nails can also be shed, the course of the disease can be extended for several months; the course of the disease often has irregular fever, chills or complications of the whole body lymph nodes heavy enlargement, toxic hepatitis, bronchopneumonia, severe cases can be secondary to infection or systemic failure skin extensive flushing, swelling, and It is one of the severe types of drug rash, mostly caused by long-term use of drugs, or continued use of drugs based on the occurrence of drug rash, the condition is progressively aggravated may be exfoliative dermatitis. Also known as erythroderma, the rash occurs on the scalp, trunk, extremities, elbows and knees, and lumbosacral area; it starts as pinhead to soybean-sized light red spots, and then develops into patches or papules with clear edges, gradually expanding and increasing to form patches, with multiple layers of silvery white scales on the surface; the rash has clear boundaries and obvious inflammation, and after scraping away the scales, a light red shiny translucent film is revealed, and then the film is scraped away to reveal a small The rash is heavy in winter and light in summer, and may be psoriasis (psoriasis) with or without self-pruritus. Oval, rose-colored, patchy rash arranged in the direction of skin lines (mostly seen in young people and adults), preferably on the trunk, neck, and proximal extremities, first occurring in the trunk a mother spot (or called the pioneer spot, shaped or oval erythema, significant inflammation, clear boundaries, uneven jagged edges, wrinkled surface, covered with bran-like scales, pale yellow or yellow-red, 2-3 cm in diameter, or larger), the mother spot appears A few days to 2 weeks later, the rapid occurrence of most child spots (shaped like the mother spot, lentil large rash or maculopapular rash), the rash is more oval, the long axis and the skin texture consistent, hair in the chest more parallel to the rib cage; rash mostly isolated mutual non-fusion, general itching is mild, the course of the disease is self-limiting, mostly one to several months, can be natural healing may be pityriasis rosea. Children, adolescent facial scaly pale spots, winter and spring obvious, initially for round, oval edge inconspicuous light red spots, 1-2 weeks after metamorphosis for light colored spots, surface dry, with gray-white bran-like scales, patches for multiple, diameter 4cm, symmetrical distribution, generally asymptomatic or mild itching, a few months can fade on its own, but can recur may be simple pityriasis, also known as white pityriasis. Preferably in the sebaceous gland distribution more parts (scalp, face, upper chest, upper back, axilla, pubic area, etc.), the basic damage is erythema, papule, surface with yellow greasy scales or scabs, symmetrically distributed, with varying degrees of itching. On the head, the lesions are patchy, with obvious exudation, often with dirty and thick yellow scabs and a foul odor; on the face, the lesions are yellow-red follicular papules and erythema with greasy scales on the surface, often accompanied by blepharitis and otitis externa; on the chest and back, the lesions are round or oval erythema of different sizes with greasy scales on the surface and clear edges; in the axillae or under the breasts of women, or in the umbilicus. The lesions on the axillae or under the breasts and umbilicus of women often show eczema-like changes, which may be seborrheic dermatitis. They appear on the neck, face, chest or back (mostly in middle-aged and elderly people), with a few flaccid blisters on the basis of erythema, with thin walls and easy rupture, revealing a superficial vesicular surface and overflowing a little plasma, forming a thin yellowish-brown crust, which dries into a leaf-like flaking, resembling exfoliative dermatitis, with a foul odor, and may have fever, chills and other systemic symptoms, probably deciduous aspergillosis. The lesions are light brown, gray-brown or light white spots and petal-like patches, the size of a soybean, with thin scales on the surface, the boundaries are clear, the lesions can fuse into a large area, the lesions are dark red after sun exposure, there are no conscious symptoms, the course of the disease is chronic, usually fading in winter, summer attacks, if not treated can last for many years may be Lichen planus (sweat spot). The onset of the disease is young, usually on the extremities and trunk, symmetrically distributed, or in severe cases may spread all over the body, manifested as dry skin, fish scale scales, the center is close to the epidermis but the edge is not slightly free, may be accompanied by palmoplantar keratosis, the symptoms are aggravated in winter, generally no conscious symptoms, or feel dry skin, itching may be ichthyosis (ichthyosis, tinea serrata).