Efficacy and Safety of House Dust Mite–Specific Immunotherapy in Patients with Atopic Dermatitis: A Retrospective Single-arm Cohort study

Objective Allergen-specific immunotherapy (AIT) has shown therapeutic efficacy in clinical trials regarding atopic dermatitis (AD). As the only currently available treatment that may potentially cure allergic diseases, AIT holds significant clinical importance. However, there is still controversy regarding the application of AIT in AD. This study evaluated the efficacy and safety of subcutaneous immunotherapy (SCIT) with mite allergens as add-on therapy in patients with AD. Methods: Ninety patients treated with SCIT for more than 3 years were evaluated using the Scoring Atopic Dermatitis (SCORAD) index, Eczema Area and Severity Index (EASI), Dermatology Life Quality Index (DLQI), and a visual analog scale for itch (VAS) in Hospital of Skin Disease (Institute of Dermatology), Chinese Academy of Medical Sciences and Peking Union Medical College from 2018 to 2023. Serum levels of total immunoglobulin E (IgE), house dust mite (HDM)–specific IgE (sIgE)-blocking factor, and HDM-specific IgG4 (sIgG4) were assessed at baseline and after 3 years. Patients were categorized into subgroups according to age, initial AD severity, and mono- or multi-sensitization. Subgroup response rates were analyzed; baseline characteristics were compared between responders and non-responders. Between-group comparisons used Student’s t-test or Wilcoxon signed-rank test as needed. Results: After 3 years of SCIT, improvement was observed in 58 patients (64.4%). Three patients (5.2%) achieved complete remission, 19 (32.8%) showed significant improvement, and 36 (62.1%) demonstrated moderate improvement. Significant reductions were observed in SCORAD, EASI, DLQI, and VAS scores. Serum levels of Dermatophagoides pteronyssinus ( Der p ) and Dermatophagoides farina ( Der f ) sIgE decreased ( P = 0.02 and P ＜0.001, respectively), whereas sIgG4 ( P < 0.001), Der p sIgE-blocking factor ( P < 0.001) and Der f sIgE-blocking factor significantly increased ( P = 0.003). Response rates were similar in patients younger than 18 years and adults (63.9% vs. 65.5%, χ2=0.02, P =0.880). Patients with moderate-to-severe AD were more likely to respond than those with mild disease (78.5% vs. 28%, χ2=20.06, P < 0.001). Multi-sensitized patients showed responses similar to those of HDM-sensitized patients (63.0% vs . 65.9%, χ2 = 0.08, P = 0.780). No significant differences were observed at baseline in sex, age, total IgE, EASI, or eosinophil count between responders and non-responders; responders had higher baseline SCORAD ( P ＜0.001), VAS ( P= 0.01), and DLQI scores ( P= 0.020) compared to no-responders. Injection-site reactions were the most common adverse events, and no serious systemic reactions occurred. Conclusion: In this real-world study, a 3-year course of subcutaneous allergen immunotherapy (SCIT) provided evidence supporting its clinical efficacy and favorable immunomodulatory effect as an add-on therapy for patients with moderate-to-severe atopic dermatitis (AD). Efficacy was consistent regardless of age or sensitization profile, and patients with more severe baseline disease were more likely to respond. SCIT exhibited a reassuring safety profile, with only minor injection-site reactions and no serious systemic events.