D3.209 - Subcutaneous Allergen Immunotherapy in Children: Frequency of Local and Systemic Adverse Reactions and Associated Risk Factors

Subcutaneous allergen immunotherapy (SCIT) is an effective immunomodulatory treatment for allergic diseases; however, it may be associated with local and systemic adverse reactions. This study aimed to evaluate the frequency of local and systemic adverse reactions following SCIT in children and to identify potential risk factors associated with reaction development.

We retrospectively reviewed 55 pediatric patients who received SCIT at the Pediatric Allergy and Immunology Clinic of Eskişehir Osmangazi University Faculty of Medicine Hospital between May 2024 and January 2026. Clinical and laboratory parameters of patients undergoing immunotherapy for venom-induced anaphylaxis or allergic rhinitis were extracted from electronic medical records. Venom immunotherapy was administered using a conventional schedule, whereas all other immunotherapies were delivered via an accelerated (rush) protocol.

The mean age of the patients was 14.3 ± 3.4 years, and 56.4% were male (n = 31). A total of 530 injections were administered. Adverse reactions occurred in 9 patients (16.4%). Among patients with reactions, 6 were receiving pollen immunotherapy, 1 house dust mite immunotherapy, and 2 venom immunotherapy. The within-group reaction rates were 17.6% for pollen immunotherapy, 8.3% for house dust mite immunotherapy, and 22.2% for venom immunotherapy, with no statistically significant difference between groups (p = 0.251). All early-phase reactions were local, with a frequency of 0.94% (n = 5). The frequency of late-phase reactions was 1.13% (n = 6), comprising late local reactions (0.57%, n = 3) and systemic reactions (0.38%, n = 2); one patient experienced an exacerbation of atopic dermatitis. Systemic reactions manifested as urticaria (grade 1, n = 1) and asthma exacerbation (grade 3, n = 1); no grade ≥4 reactions were observed. There were no significant differences between patients with and without reactions regarding age, sex, absolute eosinophil count, or total immunoglobulin E levels. However, the presence of comorbid asthma was significantly associated with adverse reactions (OR 5.14; 95% CI 1.14–23.10; p = 0.037).

SCIT is generally well tolerated in children. The presence of concomitant atopic disease, particularly asthma, appears to be an important risk factor for adverse reactions during SCIT. Closer clinical monitoring may be warranted in this subgroup.