BACKGROUND: In Amsterdam, a steep increase in positive reactions to propolis in the European baseline series was observed from 2.8% in 2020 to 16.4% in 2023. We hypothesised that this was caused by the replacement of Chinese propolis by Brazilian propolis. OBJECTIVES: To test this hypothesis and to compare rates of positive patch tests to Brazilian propolis with those to Chinese popolis. PATIENTS AND METHODS: In a prospective study, 2 commercial Chinese propolis patch test samples were tested in consecutive patients in addition to Brazilian propolis. RESULTS: Of 239 patients patch tested, 57 (23.8%) had a positive reaction to Brazilian propolis, and 9 (3.8%) to Chinese propolis. Of the 57 reactions to Brazilian propolis, only 2 (3.5%) were found to be clinically relevant, versus 3/9 (33.3%) for Chinese propolis. Patients reacting to Brazilian propolis had significantly more co-reactivities to fragrance mixes 1 and 2 and to limonene hydroperoxides than propolis B-negative individuals. CONCLUSIONS: The results confirm our hypothesis that the observed increase in positive patch tests to propolis between 2020 and 2023 was the result of the switch from Chinese to Brazilian propolis. The rates of reactions to both propolis samples from China were significantly lower than to Brazilian propolis.
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