The impact of COVID-19 on the incidence of allergic diseases in the pediatric population: A retrospective cohort study from TriNetX United States collaborative network.

Background: Allergic diseases, including asthma, allergic rhinitis (AR), and atopic dermatitis (AD), affect nearly 20% of the global population and are influenced by complex immune mechanisms. The COVID-19 pandemic, driven by SARS-CoV-2 and its evolving variants, has reshaped clinical and immunological landscapes. Previous evidence regarding the interaction between COVID-19 and allergic diseases remains inconsistent, necessitating large-scale real-world investigations. Objective: This study aimed to investigate the association between COVID-19 infection and the subsequent development of allergic diseases (AD, AR, and asthma) in pediatric populations, while exploring subgroup variations and testing robustness through sensitivity analyses. Methods: We performed a retrospective cohort study using TriNetX electronic health records from 56 U.S. healthcare facilities. Children <18 years with ≥2 visits and Polymerase chain reaction (PCR) testing (2020-2022) were included, excluding those with prior allergic disease. COVID-19 was defined by ICD-10 U07.1 and RNA positivity. Propensity score matching (1:1) balanced baseline characteristics. The primary outcome was the incident allergic disease within 1 year, assessed using Cox models; subgroup and sensitivity analyses tested robustness. Results: After matching, 412,017 patients were included in each cohort (COVID-19 vs non-COVID-19). Children with COVID-19 exhibited a significantly higher risk of developing allergic diseases (Hazard ratio (HR) = 1.211, 95% confidence interval [CI]: 1.189-1.235; P < 0.001). Elevated risks were observed across all categories: AD (HR = 1.179, 95% CI: 1.140-1.219), asthma (HR = 1.252, 95% CI: 1.216-1.290), and AR (HR = 1.223, 95% CI: 1.188-1.259). Kaplan-Meier curves demonstrated consistently higher cumulative incidence in the COVID-19 cohort. Subgroup analyses stratified by sex, age, and race yielded concordant results, while sensitivity analyses-including competing risks, extended follow-up to 2-3 years, stricter visit definitions, and exclusion of vaccinated individuals-confirmed robustness. Conclusion: COVID-19 infection was linked to a higher risk of allergic diseases in children, suggesting postviral immune dysregulation and microbiome changes as possible mechanisms. Further studies are needed to clarify causality and guide prevention and management.