National study of US emergency department visits for acute allergic reactions, 1993 to 2004

The clinical epidemiology of acute allergic reactions in the emergency department (ED) is uncertain.

To characterize ED visits for acute allergic reactions and to evaluate national trends in ED management.

The National Hospital Ambulatory Medical Care Survey was used to identify a nationally representative sample of ED visits between 1993 and 2004. Cases with a diagnosis of acute allergic reaction were identified by International Classification of Diseases, Ninth Revision (ICD-9) codes (9950, 9951, 9952, 9953, 9956).

A total of 12.4 million allergy-related ED visits occurred from 1993 to 2004, representing 1.0% (95% confidence interval, 0.93%-1.10%) of all ED visits or 1.03 million ED visits per year. The number of allergy-related ED visits remained relatively stable, averaging 3.8 per 1,000 US population per year (95% confidence interval, 3.4-4.1; P for trend = .39). Although 63% of all visits were coded as urgent, only 4% required hospitalization. Anaphylaxis coding was rare (1%). ED staff prescribed medications in 87% of visits, especially histamine, blockers (62%; P for trend = .29). Increases were noted from 1993 to 2004 for corticosteroids (22% to 50%; P < .001), histamine2 blockers (7% to 18%; P < .001), and inhaled beta-agonists (2% to 6%; P = .008). Epinephrine use was infrequent and declining (19% to 7%; P = .04).

Between 1993 and 2004, significant variability has occurred in ED management of acute allergic reactions.