Anaphylaxis is a potentially fatal disorder. In industrialized countries, the lifetime prevalence from all causes has been estimated to be between 0.05 and 2 percent in the general population and the rate of occurrence is increasing [1-6]. In the United States, the lifetime prevalence of anaphylaxis is reported to be 1.6 percent, based on strict clinical diagnostic criteria . Anaphylaxis is not always recognized as such because it can mimic other conditions and is variable in its presentation.
This topic will review the recognition and treatment of anaphylaxis by healthcare professionals working in settings such as an emergency department (ED), surgical unit, hemodialysis facility, hospital ward, clinic, or clinician's office [8-12]. Unique features of anaphylaxis in pregnant women and infants are presented separately, as is the pathophysiology of anaphylaxis. (See "Anaphylaxis in pregnant and breastfeeding women" and "Anaphylaxis in infants" and "Pathophysiology of anaphylaxis".)
DEFINITION AND DIAGNOSIS
Anaphylaxis is defined as a serious allergic or hypersensitivity reaction that is rapid in onset and may cause death [13,14]. The diagnosis of anaphylaxis is based primarily upon clinical symptoms and signs, as well as a detailed description of the acute episode, including antecedent activities and events occurring within the preceding minutes to hours.
Anaphylaxis is underrecognized and undertreated [1-3,5]. This may partly be due to failure to appreciate that it can present without obvious skin symptoms and signs and without shock. Anaphylaxis is a much broader syndrome than "anaphylactic shock," and the goal of therapy should be early recognition and treatment with epinephrine to prevent progression to life-threatening respiratory and/or cardiovascular symptoms and signs, including shock.
Diagnostic criteria — Diagnostic criteria for anaphylaxis were published by a multidisciplinary group of experts in 2005 and 2006 [13,14]. These criteria were intended to help clinicians recognize the full spectrum of symptoms and signs that comprise anaphylaxis. Recognition of the variable and atypical presentations of anaphylaxis is critical to providing effective therapy in the form of epinephrine, as well as reducing overreliance on second-line medications such as antihistamines and glucocorticoids that are not lifesaving in anaphylaxis . In a retrospective cohort study of 214 emergency department (ED) patients, these criteria were found to have a sensitivity of 97 percent compared with an allergist's diagnosis upon review of the case, as well as a specificity of 82 percent, a positive-predictive value of 69 percent, and a negative-predictive value of 98 percent .