Allergen immunotherapy safety: characterizing systemic reactions and identifying risk factors

Systemic reactions (SRs) pose a risk to those treated with subcutaneous allergen immunotherapy (AIT). The goals of the study were to calculate a rate of SRs to AIT, characterize the timing and treatment of these SRs, and analyze a case-control sample of patients for putative SR risk factors. A case-control study based on a retrospective chart review from 2004 to 2006 at a single institution was performed for patients receiving AIT. A control group received AIT over the same time period but did not have an SR. Three hundred thirty-eight patients had 10,497 AIT injection visits and 25 patients experienced 29 SRs for a rate of 0.28% per injection visit and 7.4% per patient. Gender, phase (build-up versus maintenance), asthma, angiotensin-converting enzyme inhibitors, beta-blockers, initial skin-prick test size, or allergen type did not increase the odds of an SR to AIT. Nearly one-half (48%) of the SRs occurred >30 minutes after the injection. All five patients with an abnormal physical exam or a >20% decrease in peak expiratory flow during their SRs occurred in patients presenting with their SRs >30 minutes after the injection (p = 0.02). This study found a low rate of SRs to AIT. However, a high percentage of SRs occurred >30 minutes after the injection, and many of these SRs required epinephrine. This study was unable to identify specific risk factors that predict SRs to AIT.