Toxicological trivia from 01/09/09: plants of the Family Anacardiaceae, especially Toxicodendron spp. (e.g., poison oak, poison ivy, and poison sumac or rhus)  have an active oil causing skin rash. It is:
a) Urushiol;
b) Saponin;
c) None of the above names.

Answer a. See in Spanish only; "Rhus dermatitis: an epidemic in our region progresses". Also in Wikipedia: urushiol