D3.208 - Security of initiation of SCIT in the day hospital

To assess the safety of the administration of the first dose of subcutaneous immunotherapy (SCIT) with polymerized extracts in a pediatric population and to compare the results with the safety standards established by EAACI and data from similar published studies.

A descriptive observational study was conducted through a retrospective review of pediatric patients who initiated SCIT in the day hospital during 2025. Demographic data, type of allergen extract administered, and the occurrence of adverse reactions after the first dose were collected. All immunotherapies consisted of polymerized extracts. Adverse reactions were classified as local or systemic according to commonly accepted criteria and EAACI recommendations.

A total of 83 SCIT initiations were performed, with a mean age of 11.9 years. Immunotherapy with a combination of grass pollen and olive pollen was administered in 69% of patients; 9.6% received grass pollen, olive pollen, and Cupressus; 6% received grass pollen or olive pollen; and 6% received other allergens (dog, cat, house dust mites, and Alternaria).

Local mild reactions were observed in 7.2% of patients. All reactions consisted of wheals at the injection site following the first dose of 0.2 mL. No systemic reactions were recorded. The immunotherapies associated with these reactions were mainly the combination of grass pollen and olive pollen (5 out of 6 cases) and, in one case, grass pollen alone. For subsequent doses, patients were premedicated with antihistamines and tolerated further administrations without incident.

The administration of the first dose of SCIT with polymerized extracts in a pediatric population showed an excellent safety profile. The low rate of local reactions, their mild nature, and the absence of systemic reactions are consistent with, and even more favorable than, the safety standards described by EAACI and in previously published series, supporting the initiation of SCIT in the day hospital setting as a safe procedure in children.