Corticosteroids are most effective for rashes caused by allergic or inflammatory reactions to poison ivy, metals, cloth, or other substances. Because they lower resistance to bacterial and fungal infections, they usually shouldn't be used on infected areas or wounds. However, corticosteroids are sometimes mixed with antifungal agents to help reduce itching caused by a fungus. Combinations of corticosteroids and antibiotics are seldom used because they're generally no more effective than the corticosteroids alone. Topical corticosteroids are sold as lotions, creams, and ointments.
Creams are most effective if rubbed in gently until they vanish.
In general, the ointments are the most potent. The type and concentration of corticosteroid in the preparation determines the overall strength. Stronger corticosteroid preparations require a prescription. Doctors usually prescribe potent corticosteroids first, then less potent corticosteroids as the skin heals. Generally, topical corticosteroids are applied two to three times a day in small amounts.