Poison ivy rash is caused by an allergic reaction to an oily resin called urushiol which is in the leaves, stems and roots of poison ivy, poison oak and poison sumac. It can be very itchy and last for weeks.
Poison ivy rash is a type of allergic contact dermatitis caused by an oily resin called urushiol which is found in the leaves, stems and roots of poison ivy, poison oak and poison sumac. You may get it from direct touch the oily resin, touching the contaminated objects with the oily resin, or inhaling the smoke of the burning plants with the oily resin. However, you cannot get poison ivy rash from another person with poison ivy rash unless you've touched urushiol that's still on that person or his or her clothing.