Contact allergy to dehydroabietic acid derivatives isolated from Portuguese colophony

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Abstract
7‐oxodehydroabietic acid and 15‐hydroxydehydroabietic acid were isolated as their methyl esters from Portuguese colophony of the gum rosin type and identified as contact allergen. Another oxidation product of dehydroabietic acid, 15‐hydroxy‐7‐oxodehydroabietic acid, was synthesized and identified as a component of Portuguese gum rosin. 7‐oxodehydroabietic acid was found to a be a grade III allergen according to the GPMT method. Guinea pigs induced with gum rosin showed only a low response to the isolated compounds, while patients with a known allergy to gum rosin reacted to a greater extent. The result imply that the content of oxidized dehydroabietic acids in gum rosin is too low to give a marked sensitization in the animals. However, the patients might have come in contact with the allergens in technically modified rosins. The compounds showed a pattern of cross‐reactivity in the animal experiments as well as among the patch tested patients.