Psoriasis is a chronic condition of your immune system. Typically, something triggers psoriasis to flare up and you experience the unpleasant symptoms of red, raised, scaly patches of skin. This happens because, with psoriasis, your skin cells multiply at an abnormally fast rate.
As a result, the skin builds up in patches on the surface of your body, on your scalp, elbows, knees, or other places, depending on which type of psoriasis you have.