Urushiol

Urushiol ( /ʊˈruːʃi.ɒl/) is an oily organic allergen found in plants of the family Anacardiaceae, especially Toxicodendron spp. (e.g., poison oak, poison ivy, poison sumac). It causes an allergic skin rash on contact, known as urushiol-induced contact dermatitis. The name comes from the Japanese word for the tree Toxicodendron vernicifluum (漆, urushi?). The oxidation and polymerization of urushiol in the tree's sap in the presence of moisture allows it to form a hard lacquer, which is used to produce traditional Chinese, Korean and Japanese lacquerware.