Exploring the potential benefits of allergen immunotherapy beyond respiratory allergy

Introduction: Allergen immunotherapy (AIT) is the only disease-modifying treatment for IgE-mediated allergic disorders, including allergic rhinitis and asthma, with established long-term clinical efficacy and immunological tolerance induction. Areas covered: This review synthesizes current evidence on the potential extra-allergic effects of AIT, focusing on respiratory tract infections (RTIs), SARS-CoV-2 outcomes, and selected immune-mediated conditions. AIT modulates key immunopathological pathways by promoting regulatory T and B cell responses, increasing allergen-specific IgG4, and rebalancing Th1/Th2 immunity. Emerging data suggest that these effects may extend beyond allergy control, with observational and limited clinical studies indicating reduced RTIs burden, decreased medication use, and enhanced antiviral responses, including improved interferon-mediated epithelial immunity. Preliminary findings also suggest an association between AIT and milder COVID-19 outcomes. Evidence regarding autoimmune conditions, such as alopecia areata, remains limited and largely anecdotal. Expert opinion: Although AIT demonstrates promising immunomodulatory properties beyond allergic disease, current evidence is heterogeneous and primarily observational, precluding causal inference. The broader clinical relevance of these effects remains to be established. Well-designed prospective studies integrating clinical and mechanistic endpoints are required to clarify the extent and clinical significance of AIT-induced systemic immune modulation.