Cross-reactivity between citral and geraniol - can it be attributed to oxidized geraniol?

The fragrance compound geraniol is susceptible to autoxidation when in contact with air, and to cutaneous metabolism. In both processes, the isomeric aldehydes geranial and neral are formed. Citral consists of geranial and neral. Among patients with positive reactions to citral, we have previously detected concomitant reactions to geraniol in 85% of cases and to oxidized geraniol in 73% of cases.

To study the pattern of concomitant reactions to geraniol and citral and its isomers geranial and neral, and to determine whether these isomers are important sensitizers in contact allergy to geraniol and oxidized geraniol.

The irritancy of geranial and citral was studied. Six hundred and fifty-five patients were patch tested with geranial, neral and citral at 3.5% pet., pure geraniol at 6.0% and 11.0% pet., and oxidized geraniol at 6.0% pet.

Twenty-six per cent of citral-positive patients reacted to oxidized geraniol, and 10.5% reacted to pure geraniol. Citral and/or its isomers gave positive reactions in 25% of the patients who reacted to pure geraniol.

There is little cross-reactivity between pure geraniol and citral; however, concomitant reactions to citral and oxidized geraniol were common, owing to geranial. Geranial was also the main sensitizer in the mixture citral.