Air oxidation of d‐limonene (the citrus solvent) creates potent allergens

Abstract

Products containing as much as 95% of d‐limonene are used for, e.g., degreasing metal before industrial painting and for cleaning assemblies. Experimental studies on the sensitizing potential of limonene show diverging results. In a previous study, we found that the sensitizing potential of d‐limonene increased with prolonged air exposure. The aim of 1 his study was to make further chemical analyses, to identify compounds formed by air exposure of d‐limonende and to study their allergenic potential. d‐limonene was found lo be a sensitizer after prolonged exposure to air according to 2 Freund's complete adjuvant test (FCAT) experiments and I guinea pig maximization test (GPMT) study. No significant response was obtained to d‐limonene air exposed, even if the animals were sensitized to oxidized d‐limonene. 5 main oxidation products of d‐limoncne were identified. (R)‐(–)‐carvone and a mixture of cis and trans isomers of (+)‐limonene oxide were found to he potent sensitizers, while no significant reactions were obtained m the animals induced with 8 mixture of cis and trans isomers of (–)‐carveol. It can be concluded that air oxidation of d‐limonene is essential for its sensitizing potential, and that potent allergens are created.