These can actually make the rash worse by producing their own allergic reactions when applied to already sensitive skin. Similarly, taking an oral antihistamine, such as benadryl, can help with the itching quite a bit, although it does not speed up resolution of the rash. Taking benadryl at nighttime will make most people drowsy and help them sleep through the night without itching. Again, don't use benadryl cream or spray topically, because this can cause its own reaction. Sometimes large blisters need to be drained, and sometimes an oral steroid such as prednisone may be useful.
Systemic steroids produce rapid resolution of both the itching and the rash.
If they are needed, a gradually tapering dosage over about 12 days should be given. The dosage needs to be tapered to avoid side effects after discontinuing use, and the entire course should be taken since stopping earlier may result in a rebound rash as bad as the original. Allergy shots are available to help prevent recurrences of the poison ivy, poison oak, or poison sumac rash. Unfortunately, the shots for this are frequently ineffective and should be reserved only for those who are extremely sensitive. Prescription pills containing small amounts of extract from the plants have been used for immunization.