Intended for healthcare professionals

Clinical Review

Anaphylaxis: the acute episode and beyond

BMJ 2013; 346 doi: (Published 12 February 2013) Cite this as: BMJ 2013;346:f602
  1. F Estelle R Simons, professor, department of paediatrics and child health, professor, department of immunology1,
  2. Aziz Sheikh, professor of primary care research and development2
  1. 1Faculty of Medicine, University of Manitoba, Winnipeg, Canada R3A 1R9
  2. 2Allergy and Respiratory Research Group, Centre for Population Health Sciences, University of Edinburgh, Edinburgh, UK
  1. Correspondence: F E R Simons lmcniven{at}

Summary points

  • Diagnosis is based on clinical presentation—sudden onset of characteristic symptoms in more than one body system, minutes to hours after exposure to a likely or known allergen

  • Factors associated with increased risk of severe or fatal anaphylaxis include asthma, cardiovascular disease, mastocytosis, and drugs such as β blockers

  • When anaphylaxis occurs, promptly call for help, inject adrenaline intramuscularly, and place the patient on the back or in a semi-reclining position with lower extremities raised

  • During the episode, if needed, give high flow supplemental oxygen, establish intravenous access to provide high volume fluids, and perform cardiopulmonary resuscitation

  • Provide at risk patients with adrenaline autoinjectors, personalised anaphylaxis emergency action plans, and medical identification

  • Confirm the specific trigger so that it can be avoided or allergen specific immune modulation—such as venom immunotherapy to prevent anaphylaxis from insect stings—can be carried out

Anaphylaxis is an alarming medical emergency,1 2 3 not only for the patient or caregiver, but also sometimes for the healthcare professionals involved. Although it is thought of as uncommon, the lifetime prevalence is estimated at 0.05-2%,4 5 and the rate of occurrence is increasing. Hospital admissions, although uncommon, are also increasing, as are admissions to critical care units.6 7 Many anaphylaxis episodes now occur in community settings.8 Accurate community based population estimates are difficult to obtain because of underdiagnosis, under-reporting, and miscoding, as well as use of different anaphylaxis definitions and different methods of case ascertainment in the populations studied.5 Although death from anaphylaxis seems to be uncommon, it is under-reported.9

In this article, we draw on evidence from randomised controlled trials, quasi-experimental and other observational studies, and systematic reviews. We also reference key evidence based international and national anaphylaxis guidelines and their updates.1 2 10 11

Sources and selection criteria

We based this review on Medline and …

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