D2.168 - Systemic reactions to subcutaneous immunotherapy in children

Subcutaneous immunotherapy (SCIT) is widely employed for desensitization of inhalants and hymenopteran venom allergens. While efficacious, SCIT is associated with a risk of systemic allergic reactions (SARs). Data on the safety and risk factors for SARs in children are limited. We aimed to assess the incidence and identify risk factors associated with SARs during SCIT in a pediatric cohort.

We performed a retrospective cross-sectional study of patients who received SCIT for allergic rhinitis, asthma, or Hymenoptera venom allergy during 2019-2022.

A total of 211 patients underwent 7,868 SCIT injections. Asthma prevalence was 33%; 61% of the patients exhibited polysensitization to dust mites and pollen. SARs occurred in 34 patients (16%), a prevalence of 0.4% per injection. The mean age of the patients who experienced SARs was marginally younger than of those without SARs (14.9 ± 2.9 vs. 15.7 ± 3 years, p=0.05). SARs severity was: grade 1 (23.5%), grade 2 (23.5%), and grade 3 (53%). Respiratory symptoms predominated (85%) SARs, regardless of asthma diagnosis. Dust mite extract exposure was identified as a significant risk factor (p=0.02), although most SARs occurred during March and early winter (November and December), predominantly during the maintenance phase. Delayed-onset SARs (within 60 minutes) were observed following 23% of the injections.

SARs during pediatric SCIT are not infrequent, primarily manifesting as respiratory symptoms. Dust mite allergen extract, seasonal factors, and maintenance dosing emerged as risk factors. Delayed SARs warrant attention, emphasizing the need for patient education regarding recognition and management.