Methods: We retrospectively evaluated all systemic reactions from November 1, 2004 to November 1, 2014 to determine time from injection to onset of symptoms.
Results: Of the 57,102 injections that were given over 10 years, there were 72 systemic reactions among 50 patients. Of the total number of reactions, 52.8% (38 instances) occurred after 30 minutes. Seven patients experienced symptom onset as late as 90 or more minutes post injection. The percentage of patients who required epinephrine did not differ based on reaction time (p=0.65). This dataset was unable to determine any factors predicting the likelihood of a delayed reaction such as age, sex, allergen content or duration of successful immunotherapy.
Conclusions: Our data suggest that even with a 30 minute in-office wait time, approximately half of systemic reactions occurred outside the clinic. Although in our series of patients there were few emergency treatments and no fatalities, the risk of severe reactions to allergy shots outside the clinic remains. The results underscore the importance of educating patients about the symptoms of systemic reactions, proper epinephrine self-administration, and the possibility of delayed onset of symptoms.