Is abietic acid the allergenic component of colophony?

In order to investigate whether abietic acid itself is the allergenic component of colophony, 2 commercial samples were extensively purified and tested in guinea pigs and in colophony-sensitive patients. In the modified FCAT method, sensitization was obtained with Portuguese colophony and when challenged with purified abietic acid, the animals showed no reaction. In the GMPT method, the animals were exposed to purified abietic acid. Challenging with 2 different samples of it gave no significant reaction. When patch tested, patients sensitive to colophony showed no reactions to abietic acid which had been purified immediately before the test. It is concluded that abietic acid itself is not a contact allergen.