What is Urushiol?
Urushiol is an organic oil toxin found in plants of the family Anacardiaceae, especially Toxicodendron spp. (e.g., poison oak, poison ivy, and poison sumac).
Exposure to poison ivy, poison oak, or poison sumac plants results in an allergic reaction of the skin. If the urushiol from the plant touches the skin of someone who is allergic to it, it starts a reaction that results in blisters. This reaction is known as an allergic contact dermatitis. The outbreak of the reaction starts at the spot on the skin where the urushiol touched it. Once the urushiol has been thoroughly washed off the skin, no further spread of the dermatitis can occur.