Frequency and Patterns of New Allergen Sensitization in Patients with Recurrent Allergic Symptoms During Subcutaneous Allergen Immunotherapy

Abstract

Background: Allergen immunotherapy (AIT) remains the sole disease-modifying intervention for allergic respiratory diseases. Nevertheless, symptom recurrence occurs in some patients during therapy, possibly due to new allergen sensitizations. Objective: To determine the frequency and patterns of new allergen sensitization among patients with respiratory allergic diseases who experience recurrence of allergic symptoms during subcutaneous allergen immunotherapy (SCIT). Methodology: This multicentre observational study was conducted at four healthcare centres in Rawalpindi and Islamabad, Pakistan, from January 2024 to December 2024. The study included 422 patients with allergic rhinitis and/or bronchial asthma who had received SCIT for at least two years and subsequently experienced symptom recurrence following initial improvement. Skin prick testing (SPT) was repeated to identify new sensitization patterns. Data analysis was performed using SPSS version 26. Results: Allergic symptom recurrence during SCIT was observed in 22.8% (422/1850) of patients screened. Among those with symptom recurrence, new sensitization was identified in 51.2% (216/422). Pollen sensitization was the most prevalent, occurring in 31.6% of patients, followed by sensitization to house dust mites (18.5%) and molds (12.0%). Most new sensitizations were detected in patients who experienced symptom recurrence during the third year of therapy (45.8%). No statistically significant association was observed between new sensitization and age, sex, diagnosis, or immunotherapy duration. Conclusion: New sensitization frequently develops in patients who experience symptom recurrence during SCIT. Repeating SPT to identify evolving sensitization patterns is recommended for these patients, especially for those with symptom recurrence during the third year of therapy.