5,8-dihydroxyflavone (primetin) the contact sensitizer of Primula mistassinica Michaux.

5,8-Dihydroxyflavone (primetin) has been shown to be the sensitizer in Primula mistassinica Michaux and probably the source of allergic contact dermatitis in four milkers. Its sensitizing properties as determined in guinea-pigs, are strong. As far as is known this is the first experimental demonstration of the sensitizing potency of a flavone. Presumably the flavone, with its uncommon 5,8-arrangement of hydroxy groups, is oxidized in the skin to the corresponding quinone (primetinquinone). Quinone was prepared from primetin and used for experimental sensitization of guinea-pigs. It also revealed strong sensitizing properties. Cross-reactions were obtained not only with the synthetic quinone in the flavone-sensitive animals but also with primetin in primetinquinone-sensitive guinea-pigs. Preliminary sensitization tests with other flavones have demonstrated that the whole group of flavonoid components should be taken into consideration as potential sensitizers.