Divergent Sensitization Kinetics to Indoor Allergens in Children: Early Dust Mite Surges vs Delayed Cat Dander Peaks During COVID-19 Lockdowns

Purpose: The COVID-19 pandemic altered patterns of indoor allergen exposure. However, longitudinal dynamics of sensitization kinetics across allergens remain poorly characterized. This study delineated allergen-specific sensitization dynamics during 2019-2022, contrasting responses to dust mites and cat dander. Patients and Methods: The retrospective cohort study of 43,314 children (0-17 years) in Shenzhen, China, analyzed specific IgE (sIgE) reactivity. Adjusted odds ratios (aORs) were calculated using logistic regression (adjusted for age/sex; 2019 baseline) and E-values assessed unmeasured confounding. Results: Dust mite sensitization increased significantly in 2020 (Dermatophagoides pteronyssinus\farinae aOR = 1.29\1.42, 95% CI: 1.16-1.44\1.29-1.57, both P <0.001), declined in 2021, and partially rebounded in 2022. Conversely, cat dander sensitization exhibited a delayed peak, rising significantly only by 2022 (aOR = 1.83, 95% CI: 1.30-2.65, P <0.001, E-value = 3.07). German cockroach sensitization decreased by 35% in 2022 (aOR = 0.65, 95% CI: 0.54-0.78, P <0.001, E-value = 2.26). Adolescents (6-17 years) showed heightened cat dander sensitization (2022: aOR = 2.05, P =0.001, E-value = 3.52), while males had steeper cockroach declines (2022: aOR = 0.61, P <0.001). Food sensitization remained stable except wheat (aOR = 0.80, P =0.005). Conclusion: We identify distinct allergen-specific dynamics. Dust mites acted as early-response allergens linked to confinement intensity, while cat dander emerged as delayed-response allergens likely driven by cumulative behavioral and exposure changes. Targeted environmental interventions (eg, pest control) significantly reduced cockroach sensitization. These findings advocate for allergen-tailored, time-resolved prevention strategies during public health crises, with priority protection for adolescents. Clinical Trial Registration: National Medical Research Registration Information System/MR-44-24-056093.