Psoriasis is an immune disease that occurs in about two percent of adults in western countries. About 90% of psoriasis cases is plaque psoriasis, which is characterized by “plaques”, or raised, red areas of skin covered with a silver or white layer of dead skin cells. Psoriatic plaques can appear on any area of the body, but most often appear on the scalp, knees, elbows, trunk, and limbs, and the plaques are often itchy and sometimes painful. Plaques in certain anatomical areas present particular treatment challenges, including the face, elbows and knees, scalp, and intertriginous areas (where two skin areas may touch or rub together).