Epidemiology is the study of the distribution and determinants of health-related states or events in specified populations,
and the application of this study to the control of health problems [1]. Epidemiological measures of interest for anaphylaxis
include the incidence, incidence rate, lifetime prevalence of its occurrence and case fatality rate (Box 1). Other aspects
of interest concern features of persons who experience it, temporal relationships, and the factors that lead to its development
and recurrence. Anaphylaxis is a potentially life-threatening hypersensitivity reaction to a substance or set of factors to
which the affected person is sensitive and people who experience an anaphylactic reaction remain at risk of further reactions.
Accordingly, a description of its epidemiology is important to inform the development and evaluation of strategies to reduce
its frequency of occurrence.
Anaphylaxis affects children and adults alike, but estimates of its incidence and lifetime prevalence vary across populations,
with time in the same population, and with the data sources used to estimate them. One important reason for this imprecision
relates to the great variability in clinical symptoms experienced [2]. An anaphylactic reaction can present with cutaneous,
respiratory, cardiovascular or gastrointestinal symptoms that can be misinterpreted for other disorders [3]. The variety of
physiological responses experienced by patients and the failure to identify specific biomarkers present during all attacks
contributes to the uncertainty of diagnosis [4]. Accordingly, agreement on a case definition has proved elusive and this has
contributed to difficulties of conducting research into its epidemiology [5, 6].