Background: Prevalence of positive patch test (ppt) reactions to propolis in Europe has varied with different allergen source origins. Compared with previous cycles, the North American Contact Dermatitis Group (NACDG) noted a marked increase in propolis positivity in 2019-2020. Objective: To compare propolis positivity in North American centers between 3 periods (2019, 2020, and 2021/2022), based on geographic origin and supplier. Methods: Retrospective analysis of NACDG patch test data (2019-2022) utilizing 3 different sources of propolis: Chinese propolis (Allergeaze-CPA), Chinese propolis (Chemotechnique-CPC), and Brazilian propolis (Allergeaze-BPA). Results: Proportions of ppt reactions to propolis were: 3.7% (84/2260) to CPA in 2019, 14.7% (271/1838) to BPA in 2020, and 2.2% (66/3052) to CPC in 2021/2022. There was a statistically significant difference in prevalence of reactions for BPA compared with both CPA and CPC (P < 0.00001). Conclusions: When unexpected changes are noted in patch test positivity, especially with naturally derived allergens, the reasons behind those changes should be investigated. The substitution of Brazilian for Chinese propolis resulted in a significant increase in ppt reactions.
