These plants contain the oil urushiol on their surfaces. Once the urushiol gets down into your skin, oxidation in the skin cells turns it into a reactive quinone, which then reacts to and binds the molecules on the outside of your skin cells. read more
Also, the urushiol toxin in poison ivy is not killed by fire. As a result, being exposed to or inhaling the smoke from burning poison ivy can cause a severe allergic reaction, inside the body as well as on the skin. read more