Effectiveness and Predictors of House Dust Mite Subcutaneous Immunotherapy in Polysensitised Patients With Allergic Rhinitis: A Multicentre Retrospective Study

Background In China, therapeutic options are limited by the narrow availability of allergen preparations, with house dust mite (HDM) allergen immunotherapy (AIT) as the main choice for most patients. However, polysensitization is highly prevalent, and the benefit of HDM AIT in such patients remains uncertain. The study aims to evaluate the effectiveness of single‐allergen HDM AIT on both perennial and coexisting allergen‐specific symptoms in polysensitised allergic rhinitis (AR) patients and to explore predictors of treatment response. Methods We performed a multicenter retrospective cohort study including 81 patients with AR who were polysensitised to HDM and at least one other inhalant allergen (e.g., pollens, mould or animal dander). All participants received HDM subcutaneous immunotherapy (SCIT) for 12 to 36 months. Baseline characteristics, including serum allergen‐specific IgE (sIgE) levels and comorbidities, were collected. Symptom severity was assessed using the Visual Analog Scale (VAS), and treatment response was defined as a ≥ 30% reduction in VAS scores from baseline. Statistical comparisons between responders and non‐responders were conducted using Fisher's exact test for categorical variables and Mann–Whitney U tests for continuous data. Firth logistic regression was used to identify predictors of treatment response. Results The overall response rate for perennial symptoms was 68.8%, and varied in patients with co‐existing allergies: 72.7% for moulds, 70.0% for animal dander, 65.5% for tree pollen, 70.2% for weed pollens. Allergen‐specific symptom response rates varied across allergens: 68.2% for moulds, 30.0% for animal dander, 56.7% for tree pollens, 74.5% for weed pollens. Higher sIgE levels to HDM and mould were significantly associated with lower response rates in patients co‐sensitised to both. A predictive model incorporating both sIgEs showed good specificity. Conclusion Single‐allergen HDM AIT is effective in many polysensitised AR patients; however, its efficacy varies by coexisting allergen type and sIgE level. Patients co‐sensitised to mould with high HDM and mould sIgE appeared to have poorer outcomes. These preliminary findings require confirmation in larger prospective studies to guide tailored AIT strategies.