Contact allergy due to colophony. (V). Patch test results with different types of colophony and modified-colophony products.

The results of patch tests with colophony in the standard series between 1983 and 1987 were analyzed. 5521 patients were tested in the Department of Dermatology, Hamburg, while 354 were tested in other clinics and private practices. Colophony was positive in 2.4% and 11.9%, respectively. Out of 62 patients in the 1st group and 75 in a 2nd group tested subsequently with 6 unmodified types of colophony and 12 types of modified-colophony products, 17 did not react to the unmodified material. However, most of them responded to 1 or more of the modified products. In the enlarged group (n = 75), reactions to Abitol and the maleic-modified products were the most frequently obtained. As the authors are convinced that the actual incidence of allergic reactions to modified-colophony products is underestimated, they propose to test a mixture of 3 materials: Chinese colophony (today 50% of the world market) and 2 derivatives (modified colophony), instead of the 60% mix of unmodified colophony, in the standard series.