What Is Psoriasis?

Psoriasis is a chronic (long-lasting) skin disease characterized by scaling and inflammation. Scaling occurs when cells in the outer layer of skin reproduce faster than normal and pile up on the skin's surface.
Psoriasis affects 2 to 2.6 percent of the United States population, or almost 5.8 to 7 million people. It occurs in all age groups and about equally in men and women. People with psoriasis may suffer discomfort, restricted motion of joints, and emotional distress.
When psoriasis develops, patches of skin thicken, redden, and become covered with silvery scales. These patches are sometimes referred to as plaques. They may itch or burn. The skin at joints may crack. Psoriasis most often occurs on the elbows, knees, scalp, lower back, face, palms, and soles of the feet. The disease also may affect the fingernails, toenails, and the soft tissues inside the mouth and genitalia. About 10 percent of people with psoriasis have joint inflammation that produces symptoms of arthritis. This condition is called psoriatic arthritis.
Psoriasis is not contagious in any way. It is not possible to "catch" psoriasis by touching a person afflicted with it.