Urushiol is any of several chemicals found in plants of the family
Anacardiaceae, especially
Toxicodendron, such as
poison ivy, and causing the rash on contact. It is named for
urushi[?], a
lacquer produced by
Japanese from the sap of
Toxicodendron trees called
kiurushi. Chemically it is 1-alkyl phene-2,3-ol; the alkyl group has 15 or 17 carbons and may be unsaturated, depending on species.
External link: http://waynesword.palomar.edu/ww0802.htm