Psoriasis is a term that encompasses a group of chronic skin disorders that affect any part of the body from the scalp to the toenails, but most frequently affect the scalp, elbows, knees, hands, feet and genitals. Over seven million men and women in the U.S. of all ages have some form of psoriasis, which may be mild, moderate or severe. In addition it may be categorized into different types: plaque, pustular, erythrodermic, guttate or inverse psoriasis. Most forms involve an itching and/or burning sensation, scaling and crusting of the skin. Type-specific symptoms include:

• Plaque psoriasis (the most common type): raised, thickened patches of red skin covered with silvery-white scales.
• Pustular psoriasis: pus-like blisters.
• Erythrodermic psoriasis: intense redness and swelling of a large part of the skin surface.
• Guttate psoriasis: small, drop-like lesions.

Inverse psoriasis: smooth red lesions in the folds of the skin.

While the cause of psoriasis has yet to be discovered, suspected triggers include emotional stress, skin injury, systemic infections and certain medications. There is a possibility that susceptibility to psoriasis is inherited.