Temporal changes in allergen-specific IgE sensitization patterns in Xiamen, 2019-2023: a retrospective...

The COVID-19 pandemic has induced substantial changes in environment, lifestyle, and health behaviors. We observed temporal associations between the pandemic period and declining sIgE positivity rates; however, causality cannot be established due to the retrospective observational design. Distinguishing between asymptomatic sensitization (positive specific IgE without clinical symptoms) and true allergic disease remains critical. This study aims to describe the trends in allergen-specific IgE (sIgE) positivity-as a marker of sensitization-in the Xiamen population from 2019 to 2023, a surrogate marker of sensitization that does not equate to clinical allergy, providing insights into population-level immunological changes during the pandemic.

We performed a retrospective cross-sectional analysis of 3,207 serum sIgE testing records (3,210 initial records minus 3 exclusions) from patients who underwent allergen screening at our hospital between January 2019 and December 2023. These records include repeated tests from some individuals; a subset of 2,784 records from 2,750 unique patients was used for GEE modeling to account for within-individual correlation. Data on sensitization to inhalant allergens (e.g., dust mites, cat dander, cockroach) and food allergens (e.g., egg white, crab, milk) were analyzed. Age and sex distributions were examined, though detailed information on clinical symptoms (e.g., eczema, rhinitis), comorbidities, and longitudinal follow-up of individual patients was not available.

Among 3,207 testing records, 1,454 (45.34%) were positive for sIgE to one or more allergens. The annual positivity rate declined sharply from 76.07% (89/117) in 2019 to 32.26% (519/1,609) in 2023 (p < 0.001). Dust mites were the most prevalent inhalant allergens, with about a third of all testing records showing sensitivity (35.30%, 1,035/3,207), followed by cockroach and cat hair. For food allergens, egg white, crab, and milk ranked highest. Males showed higher positivity rates for both inhalant and food allergens compared to females, and the difference was statistically significant (p < 0.01). Most allergens showed age-related differences, with the exception of cat hair, dog epithelium, crb and ragweed; cockroach showed statistically significant differences across age groups (χ ² = 32.89, p < 0.001). We observed temporal associations between the pandemic period and declining sIgE positivity rates; however, these findings should be interpreted with caution due to the observational study design and potential selection bias.

This study documents a significant decline in sIgE positivity rates for both inhalant and food allergens in Xiamen from 2019 to 2023. To our knowledge, this is the first report from Xiamen spanning the full COVID-19 pandemic period, providing foundational data for future hypothesis-driven research. Sex- and age-specific differences in sensitization patterns were observed. However, based on the current dataset alone, it is not possible to determine whether these changes reflect true shifts in clinical allergic disease or result from alterations in testing practices, population composition, or other confounders. Future research must integrate detailed clinical phenotyping (including age-stratified symptom data, comorbidities such as eczema, and longitudinal follow-up) and lifestyle/environmental measurements to identify modifiable factors for preventing allergy development-not merely managing sensitization.