Psoriasis is a non-contagious common skin condition that causes rapid skin cell reproduction resulting in a red, itchy scalp, dry patches of thickened skin. The dry flakes and skin scales are thought to result from the rapid build-up of skin cells. Psoriasis commonly affects the skin of the elbows, knees, and scalp. Psoriasis can be caused by a variety of reasons. Heredity can be crucial.