Post–COVID-19 onset of allergic conditions in a propensity-matched cohort of children and adults

Background SARS-CoV-2 offers a new context to evaluate the relationship between viral infection and allergic disease. A biologically plausible mechanism exists for postinfectious type 2 helper T cell–skewed responses, among other forms of immune dysregulation; early studies suggest increases in asthma and other allergic or atopy-associated diagnoses after infection. Objective To investigate whether COVID-19 infection predisposes individuals to developing allergic conditions. Methods We conducted a 1:2 propensity-matched retrospective cohort study of individuals aged 1 to 64 years, evaluating the association between COVID-19 exposure and the development of incident allergic conditions (atopic dermatitis, asthma, food allergies, rhinoconjunctivitis, medication allergies, or urticaria) within a follow-up period of 18 months. We calculated hazard ratios for the incident outcomes of interest among the entire cohort, and in subanalyses of children and active-duty service members. Results COVID-19 infection was associated with significantly increased hazard ratios for all six allergic conditions in the full cohort. Among the active-duty subset, asthma and rhinoconjunctivitis were significantly associated with infection. In children, all conditions except food allergy were significantly associated with infection. Higher sponsor rank, evaluated as a potential surrogate for socioeconomic status, showed a slight protective effect against the development of asthma. Conclusion This study adds to the growing body of evidence illustrating the risk of developing allergic conditions after COVID-19 infection in both children and adults. Our findings highlight the potential public health burden of these conditions, emphasize the importance of monitoring for allergic diseases after COVID-19 infection to enable prompt intervention, and suggest a mechanistic link between COVID-19 infection and type 2 inflammation.