Washing all exposed areas of the skin for at least 10 minutes and applying calamine lotion is a treatment for poison ivy, states WebMD. Self-care treatments are usually sufficient for mild poison ivy rashes, states Mayo Clinic.
Applying a cold compress for 15 to 30 minutes several times a day can also help treat poison ivy rashes, states WebMD. Taking a cool shower or using oral antihistamines can help the itching associated with poison ivy. It is also important to wash all clothing the person was wearing to prevent future rashes. If the rash is severe or widespread, a doctor may prescribe corticosteroids to deal with the rash, states Mayo Clinic.