Psoriasis is an autoimmune skin disease that causes scaling, skin redness and irritation. Psoriasis causes red, scaly patches that are generally found on the elbows, fingernails, scalp, palms, knees, face, feet and inside the mouth. Factors that can trigger psoriasis include infections, heavy alcohol consumption, cold weather, certain medications, smoking, stress and injury to the skin such as bug bite, cut and sever sunburn. The signs and symptoms of psoriasis vary from person to person which includes dry, cracked skin that may bleed, red patches of skin covered with silvery scales, small scaling spots, itching, burning, swollen and stiff joints.