Corticosteroids--These drugs reduce inflammation and the turnover of skin cells, and they suppress the immune system. Available in different strengths, topical corticosteroids (cortisone) are usually applied to the skin twice a day. Short-term treatment is often effective in improving, but not completely eliminating, psoriasis. Long-term use or overuse of highly potent (strong) corticosteroids can cause thinning of the skin, internal side effects, and resistance to the treatment's benefits. If less than 10 percent of the skin is involved, some doctors will prescribe a high-potency corticosteroid ointment. High-potency corticosteroids may also be prescribed for plaques that don't improve with other treatment, particularly those on the hands or feet. In situations where the objective of treatment is comfort, medium-potency corticosteroids may be prescribed for the broader skin areas of the torso or limbs. Low-potency preparations are used on delicate skin areas. (Note: Brand names for the different strengths of corticosteroids are too numerous to list in this booklet.)