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 its 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‐δ¹³⁽¹⁴⁾‐dihydroabietic acid and 12 α‐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 oxidation products for patch testing in the diagnosis of contact allergy to colophony.