Mild cases of poison sumac are treatable at home using a cold compress and medication to relieve itching, according to WebMD. More serious cases with more extensive rashes require medical evaluation and possibly prescription medication.
The oil in poison sumac causes a contact rash, notes WebMD. This rash is usually mild and occurs after exposure to the plant. Treatment for a mild rash requires applying a wet cloth to the area or soaking in a tub of cool water. Calamine lotion, available at any drug store, can be applied to provide relief from the rash's itch. Not scratching the area is important, as scratching can lead to a skin infection. Antihistamines, topical anesthetics and topical antibiotics should be avoided, as these can cause additional problems.
Rashes caused by poison sumac that cover a large portion of the body or that cause extreme itching should be evaluated by a doctor. If needed, a doctor can prescribe a corticosteroid cream to help reduce symptoms and clear up the rash. In addition, severe rashes may require corticosteroid injections or medications taken by mouth.
To lessen the chance of developing a rash, washing the skin after exposure to poison sumac can help. All clothing exposed to poison sumac should be laundered right away.