Co‐Reactivity of Fragrances and Fragrance‐Markers in Patients With Positive Patch Tests to Chinese and Brazilian Propolis

BACKGROUND: In patients with contact allergy to Chinese propolis, co-reactivity to the four fragrance markers present in the European baseline series ( Myroxylon pereirae resin [balsam of Peru], colophonium, fragrance mixes 1 and 2) has been well documented. The co-reactivity pattern of Brazilian propolis has not yet been sufficiently analysed. OBJECTIVES: To investigate co-reactivity patterns to the fragrance markers and to the fragrances linalool hydroperoxides and limonene hydroperoxides in patients reacting to Chinese and Brazilian propolis. MATERIALS AND METHODS: Retrospective analysis of patch test results in a cohort of 701 patients tested with Chinese propolis and a cohort of 2509 individuals tested with Brazilian propolis investigated in Amsterdam during 2019-2025. RESULTS: For Chinese propolis, we found significant associations with the four fragrance markers and limonene hydroperoxides. For Brazilian propolis, there were significant associations with all four fragrance markers and both limonene and linalool hydroperoxides. There were indications of a closer relationship between Brazilian propolis and fragrances than of Chinese propolis and fragrances, possibly resulting in many more positive patch test reactions to the Brazilian variety. CONCLUSIONS: Significant co-reactivity to fragrances and -marker(s) was confirmed for patients allergic to Chinese propolis and established for patients with positive patch tests to Brazilian propolis.