Poison ivy rash is caused by an allergic reaction to an oily resin called urushiol (u-ROO-she-ol). This oil is in the leaves, stems and roots of poison ivy, poison oak and poison sumac.

Wash your skin right away if you come into contact with this oil, unless you know you're not sensitive to it. Washing off the oil may reduce your chances of getting a poison ivy rash. If you develop a rash, it can be very itchy and last for weeks.

You can treat mild cases of poison ivy rash at home with soothing lotions and cool baths. You may need prescription medication for a rash that's severe or widespread — especially if it's on your face or genitals.

Aug. 11, 2015