Contact allergy to colophony. (IV). The sensitizing potency of commercial products. An investigation of French and American modified colophony derivatives.

The sensitizing capacity of 15 commercial colophony products was studied experimentally in guinea pigs. The study included 8 French and 6 American colophony derivatives as well as French tall oil colophony. The results indicate that tall oil colophony is the strongest sensitizing material within the tested group and that the maleic-modified products and the zinc-calcium-resinate are moderate sensitizers. Most of the modified products show a higher sensitizing capacity than the genuine resin acids themselves. Cross-reactions between the resin acids and the derivatives are uncommon. Therefore, patch testing with high concentrations of colophony (e.g., 60%) will not help to detect patients with colophony-derivative allergy.