Systemic Allergic Reactions to Subcutaneous Allergen Immunotherapy-A Single-Center Experience

Area of Science:

• Immunology
• Allergy and Clinical Immunology
• Pharmacovigilance

Background:

• Allergen immunotherapy (AIT) is a recognized treatment for allergies.
• Systemic reactions (SRs) are the most significant adverse events in AIT, despite their low incidence.
• Subcutaneous allergen immunotherapy (SCIT) requires careful monitoring for SRs.

Purpose of the Study:

• To determine the frequency and characteristics of SRs in SCIT.
• To identify potential risk factors associated with SCIT-induced SRs.

Main Methods:

• Retrospective analysis of 47,982 SCIT injections from 317 patients (2019-2024).
• Inclusion of patients with allergic rhinitis or venom allergies who experienced SRs.
• Classification of SRs using the World Allergy Organization (WAO) SCIT SR Grading System.

Main Results:

• SRs occurred in 26 patients (8.2%), with an incidence of 0.05% per injection.
• Asthma was present in 42.3% of patients; 30.8% had prior SCIT reactions.
• Higher serum specific IgE/total IgE ratio correlated with more severe SRs; prior reactions linked to milder SRs.

Conclusions:

• SRs to SCIT are infrequent, and severe reactions are rare.
• Elevated serum specific IgE/total IgE ratio is a risk factor for severe SRs.
• Pre-treatment risk-benefit assessment is crucial, especially for patients with identified risk factors.