Contact allergy due to colophony (VI). The sensitizing capacity of minor resin acids and 7 commercial modified-colophony products.

3 minor resin acids and 7 commercial modified-colophony products of different origins were studied by experimental sensitization by means of a modified FCA method. All 3 resin acids were almost negative. The commercial products gave different results. While the maleic-modified product of Greek origin showed a strong sensitizing power, the fumaric-modified, terpene-phenol-modified and a disproportioned rosin were only moderate. A remarkable difference was obtained with the Swedish and Finnish tall oil rosins, which, in contrast to the previously studied French product, exhibited only a weak sensitizing capacity.