Psoriasis, chronic recurring disease of the skin, characterised by the appearance of plaques, patches, or papules on the skin surface. The lesions are usually slightly elevated above the normal skin surface, sharply distinguishable from normal skin, and red to reddish-brown in colour. They are usually covered with small whitish-silver scales that adhere to the underlying eruption and, if scraped off, leave bleeding points. The extent of the disease may vary from a few tiny lesions to generalised involvement of most of the skin. Characteristically the elbows, knees, scalp, and chest are involved.
The cause of the disease is unknown, though unusually rapid turnover of cells in the epidermis (three to four days compared with three weeks normally) has been observed. It almost never occurs in persons of naturally dark skin pigment, and the affliction is often seen to run in families. A variety of preparations applied locally may be helpful, and the rash often subsides on exposure to sunlight. In 1979 a successful treatment for severe, chronic psoriasis was introduced. It consists of first coating the skin with a dye that absorbs ultraviolet light and then shining ultraviolet light on the painted area. Because this technique causes an increased incidence of mild skin cancers, it is reserved for severe cases of psoriasis.
Herbs & Psoriasis