Psoriasis is a chronic, autoimmune disease of the skin and joints, characterized by raised, red patches (plaques) covered with an often thickened silvery-white scale. Normally skin replaces itself every 27-30 days, however, in psoriasis the skin turns over every 5-6 days. It should be noted that while the cells are dividing more rapidly, similar to cancer cells, they do not become malignant. Psoriasis occurs most often on the extensor areas of the body such as elbows and knees and back of the scalp. The average age of onset is 27 but it may first appear in infancy or in old age. It affects approximately two percent of the world’s population. Psoriasis is not contagious.