Age-Related Differences in Efficacy and Safety of Subcutaneous Immunotherapy in Allergic Rhinitis: A Real-World Study.

Objective: To investigate age-related differences in efficacy and safety of subcutaneous immunotherapy (SCIT) among patients with allergic rhinitis (AR). Study design: Retrospective cohort study. Setting: Tertiary referral center. Methods: AR patients who completed a 3-year course of dust mite SCIT with a 2-year post-SCIT follow-up were categorized into pediatric and adult groups. Baseline characteristics, SCIT efficacy, and adverse reactions were compared between groups. Multivariable logistic regression was used to identify independent predictors of SCIT efficacy and adverse reaction. Results: 889 patients were included, comprising 544 children and 345 adults. Adults exhibited higher baseline symptom burden, higher rates of former or current smoking and alcohol consumption, longer AR duration, more frequent dose adjustments during SCIT, and greater prevalence of comorbid asthma and urticaria. In contrast, children had higher frequencies of family history of allergy, monosensitization, food allergy, and secondary immunotherapy. Multivariable logistic regression confirmed that older age, particularly adult status, was an independent risk factor for reduced SCIT efficacy at both 1 and 2 years post-SCIT discontinuation, after adjusting for clinical confounders. Adverse reactions, including both local and systemic events, occurred more frequently in children, though the majority were mild and occurred during the maintenance phase. Notably, older or adult age was independently associated with a lower risk of SCIT-related adverse reactions. Conclusion: Pediatric patients demonstrated superior short- and long-term SCIT efficacy compared to adults, along with a higher incidence of adverse reactions. These results support age-specific strategies to maximize clinical benefits and minimize risks in SCIT for AR.