Reynolds G, Epstein W, Terry D, Rodriguez E
Contact Dermatitis. 1980 Jun;6(4):272-4. doi: 10.1111/j.1600-0536.1980.tb04929.x.
The major contact allergen of Phacelia crenulata (Hydrophyllaceae) has been identified as geranylhydroquinone. A maximization test of geranylhydroquinone showed this to be a potent sensitizer comparable in degree to poison oak/ivy urushiol. Comparative patch testing on humans with urushiol established that the phacelia allergen does not cross-react with poison oak or ivy.
