Psoriasis is a skin disease that causes scaling and inflammation (pain, swelling, heat, and redness). Skin cells grow deep in the skin and slowly rise to the surface. This process is called cell turnover, and it takes about a month. With psoriasis, it can happen in just a few days because the cells rise too fast and pile up on the surface. Most psoriasis causes
patches of thick, red skin with silvery scales. These patches can itch or feel sore. They are often found on the elbows, knees, other parts of the legs, scalp, lower back, face, palms, and soles of the feet. But they can show up other places such as fingernails, toenails, genitals, and inside the mouth.