The Oil in Poison Ivy That Causes a Rash
Puzzle 20 of Tolkien Universe Medium Pack
Question is: The Oil in Poison Ivy That Causes a Rash
and the answer is: URUSHIOL
Word Meaning:
URUSHIOL — (organic chemistry) An oil found in plants of the family Anacardiaceae, causing an allergic skin rash on contact; consists of a variable mixture of several related organic compounds.
Definitions from Wiktionary.