Poison ivy and other poisonous plants are no laughing matter. If you develop a reaction, soothe the itch with a cool shower and apply calamine lotion. If the rash is severe, your doctor may suggest an antihistamine or steroidal medicines to reduce the itching and redness. To help eliminate the offending allergen, try a warm soapy bath. Scrub under your nails to remove any traces of the allergen and put the clothes you were wearing when you came into contact with the plant in a hot cycle wash. Once healing begins, keep the area well hydrated with a non-sensitizing, hypo-allergenic moisturizer.