Sublingual immunotherapy (SLIT) has been widely established as a disease-modifying treatment for allergic airway diseases. However, its efficacy and safety in allergic pharyngitis (AP) remain insufficiently investigated and require further clinical validation.

In this retrospective study, 100 patients diagnosed with house dust mite (HDM)-induced AP concomitant with allergic rhinitis (AR) were enrolled. All participants received standardized SLIT for three consecutive years. Clinical outcomes, including total pharyngolaryngeal symptom score (TPLSS), total nasal symptom score (TNSS), total medication score (TMS), visual analog scale (VAS) scores, and quality of life measures, were systematically assessed at baseline and subsequently at 3 months, 6 months, 1 year, 2 years, and 3 years post-treatment initiation. Safety was evaluated through adverse events (AEs).

Compared to the baseline, patients with AP accompanied by AR exhibited significant improvements in both pharyngeal and nasal symptoms during the follow-up, with a reduction in symptomatic medication use and an improvement in quality of life. Subgroup comparisons revealed no significant difference in efficacy between mono- and poly-sensitized patients. Furthermore, a positive correlation was observed between nasal and pharyngeal symptoms (R2 = 0.44, P < 0.001). Major AEs occurred primarily within the first three months, and no serious AEs were reported.

Three years of HDM-SLIT may alleviate both pharyngeal and nasal symptoms in patients with AP and AR, thereby expanding the application of SLIT in the treatment of airway allergic diseases.