Real-world outcomes of personalized sublingual immunotherapy for environmental allergies delivered through a telemedicine platform: a retrospective longitudinal cohort study

Background Allergen immunotherapy (AIT) is a disease-modifying treatment for IgE-mediated respiratory allergy, but real-world use is limited by access and adherence. Telemedicine-enabled sublingual immunotherapy (SLIT) may address these barriers; long-term outcomes remain incompletely characterized. Methods Retrospective longitudinal cohort study of adults receiving personalized SLIT via a telemedicine platform (2020–2025). Participants with ≥1 baseline and ≥1 follow-up after ≥12 months of treatment were included ( n = 2,897). Outcomes included symptom severity, medication use, quality of life (QoL), adherence, and adverse events. Longitudinal changes were analyzed using mixed-effects models; asthma subgroup analyses were performed. Results Mean age was 39.0 years, 52.7% were female, and 25.3% had asthma. Median follow-up was 20 months. Symptom severity decreased, with a 10.1-point reduction at 6 months and smaller subsequent declines. Clinically meaningful improvement (≥30-point reduction) increased from 28% at 12 months to 45% at 24 months; higher baseline severity predicted earlier response (HR 2.95). Medication use declined over time (OR 2.31 per 12 months), with fewer medication categories used. QoL improvement increased from 81.4% at 12–18 months to 90.7% at 30–36 months (OR 4.68 per 12 months). Self-reported adherence was high (>90% for ≥20 days/month), and discontinuation was uncommon. Adverse events were infrequent and predominantly mild (Grade I: 11.7%); no anaphylaxis or eosinophilic esophagitis was reported. Among patients with asthma, longer treatment duration was associated with improved control, reduced inhaler use, and improved QoL. Conclusions Personalized SLIT delivered via telemedicine was associated with sustained symptom improvement, reduced medication use, high adherence, and a favorable safety profile, supporting the feasibility and scalability of this care model in routine clinical practice.