Can Epinephrine Coated Syringe for Subcutaneous Immunotherapy (SCIT) Reduce Large Local Reaction?

Allergen immunotherapy (AIT) is an immune mediated treatment which modifies T helper (Th) 2-directed response through the interplay between regulatory T and B cells, blocking IgG4 antibodies and tissue effector-mediated mechanisms. Aeroallergen immunotherapy is recommended for patients with allergic rhinitis, allergic conjunctivitis or allergic asthma whose symptoms were not adequately controlled by antigen avoidance and pharmacotherapy. AIT could reduce symptoms and medication usage in respiratory allergy. In children, AIT prevented the progression from allergic rhinitis to asthma and prevented new onset of allergen sensitization in monosensitized patients. The administration of allergen by subcutaneous injection (SCIT) is a common practice among allergists.

The benefits of SCIT must be weighed against the risks of side effects which can be mild or life threatening. Adverse allergic reactions to SCIT were classified as either local (LR) or systemic reactions (SR).6 Large local reactions (LLR) are defined as erythema and/or swelling (> 25 mm) at the site of injection. The timing of adverse reactions were categorized into immediate (occurring within 30 min) and late reactions (occurring > 30 min after injection). LR associated with SCIT ranged from 26-72% of patients and 0.7-4% of injections. SR were reported to occurred in 3.7% of patients and 0.3% of injection. Recent prospective study in pediatric patients who received SCIT showed immediate LR in 54.6%, delayed LR in 56.1%, immediate SR in 2.2% and delayed SR in 7.4% of the patients. Severe SR were seen in 0.03% of all treatments which appeared within 30 minutes after the injections. The author concluded that children had similar rates of LR compared to adult patients but had lower rates of severe SR.

Several studies indicated that individual LR did not predict subsequent SR. The rate of SR were not change despite the dose adjustment after a LR. However, patients with greater frequency of LLR might be at an increased risk for future SR. Recognizing the significance of frequent LLRs is important for designing safer protocols for successful SCIT.

In the Division of Allergy and Clinical Immunology, Department of Pediatrics, Faculty of Medicine Siriraj Hospital, Mahidol University, we performed SCIT in approximately 100 patients and 2000 injections per year. The LR associated SCIT were complained in 75% of the patients. Of the patients who experienced LR, 80% had LR more than 25 mm which was considered LLR.

Many strategies to prevent or minimize LR were reported. Oral antihistamines, leukotriene receptor antagonist (LTRA) or anti-IgE could reduce LR during the built-up phase. Cold compression or topical steroid were used to reduce the LR without any strong evidence. To our knowledge, the benefit of epinephrine coated syringe prior to drawing the allergen extract for SCIT in patients with frequent LLR has never been explored in any controlled trial.