Psoriasis is a long-lasting, noncontagious autoimmune disease characterized by patches of abnormal skin.[4][5] These areas are red, pink, or purple, dry, itchy, and scaly.[8][3] Psoriasis varies in severity from small localized patches to complete body coverage.[3] Injury to the skin can trigger psoriatic skin changes at that spot, which is known as the Koebner phenomenon.[9]