Thirty-six images of Poison Ivy, Toxicodendron radicans, Rhus radicans, Anacardiaceae, Cashew Family, a vine, often climbing, best known for causing severe contact dermatitis. Internal consumption of Poison Ivy may cause severe effects, necessitating steroid or other therapies. Smoke from the burning plant and dried plant specimens can still cause dermatitis. Highly variable in form and habit, poison ivy is the best–known of all poisonous plants in North America. Fifty percent of the population is allergic to the plant, which causes, painful, irritating contact dermatitis. All plant parts (especially the sap) contain irritant, non-volatile, phenolic substances referred to as urushiol or toxicodendrol. Found in resin canals, the oily mixture is released when the plant is bruised, even slightly. The toxins can bind to skin proteins, resulting in the typical reaction many people experience.