Contact allergy due to colophony. (IX). Sensitization studies with further products isolated after oxidative degradation of resin acids and colophony.

Degradation of abietic, levopimaric and dehydroabietic acids after exposure to air and light over a period of one to several months, as well as examination of degraded French tall oil rosin and Portuguese colophony, led to the isolation of numerous oxidation products. These compounds were synthesized and consigned to experimental sensitization in guinea pigs. From 20 substances studied as acids or as their methyl esters, in the present and preceding paper, at least 2 can be named: 8,12-peroxydo-delta 13(14)-dihydroabietic acid and 12 alpha-hydroxyabietic acid, that contribute a great deal to colophony allergy by both their sensitizing capacity and their determined concentration in the mixture of degradation products. We recommend the preparation of a new mixture of colophony oxidation products for patch testing in the diagnosis of contact allergy to colophony.