Anaphylaxis

Last reviewed: 27 Oct 2022
Last updated: 05 May 2022

Summary

Definition

History and exam

Key diagnostic factors

  • acute onset
  • airway swelling (angio-oedema)
  • inspiratory stridor and hoarse voice
  • shortness of breath
  • wheezing, chest hyperinflation, and accessory muscle use
  • cyanosis
  • respiratory arrest
  • pale, clammy skin
  • hypotension
  • increased pulse rate (tachycardia)
  • bradycardia
  • cardiac arrest
  • confusion or disorientation
  • urticaria (hives)
  • erythema
  • pruritus
  • angio-oedema
  • rhinitis
  • bilateral conjunctivitis
Full details

Other diagnostic factors

  • risk factors
  • nausea, vomiting, diarrhoea, and incontinence
  • abdominal cramps and pain
  • agitation, anxiety, and a sense of impending doom (angor animi)
Full details

Risk factors

  • adult age: food-, insect venom- and medicine-related
  • <30 years old: food-associated, exercise-induced
  • female sex
  • atopy/asthma
  • history of anaphylaxis
  • exposure to a common sensitiser (e.g., latex)
Full details

Diagnostic investigations

1st investigations to order

  • mast cell tryptase
  • 12-lead ECG
  • urea and electrolytes
  • arterial blood gases
Full details

Investigations to consider

  • chest x-ray
Full details

Treatment algorithm

INITIAL

presumed anaphylaxis: in cardiorespiratory arrest

presumed anaphylaxis: not in cardiorespiratory arrest

ACUTE

after initial treatment: not in cardiorespiratory arrest

ONGOING

post-anaphylaxis

Contributors

Expert advisers

Alexander Alexiou, MB BS BSc DCH FRCEM Dip IMC RCSEd

Emergency Medicine Consultant

Barts Health NHS Trust

Physician Response Unit Consultant

London’s Air Ambulance

Royal London Hospital

London

UK

Disclosures

AA declares that he has no competing interests.

Thomas Palmer, BSc MBChB FRCEM

ST6 Emergency Medicine

Royal London Hospital

London

UK

Disclosures

TP declares that he has no competing interests.

Acknowledgements

BMJ Best Practice would like to gratefully acknowledge the previous team of expert contributors, whose work has been retained in parts of the content:

Doerthe Adriana Andreae MD

Assistant Professor

Pediatric Allergy and Immunology

Penn State Health Milton S. Hershey Medical Center

Hershey

PA

Michael Henning Andreae MD

Associate Professor

Department of Anesthesiology

Penn State Health Milton S. Hershey Medical Center

Hershey

PA

Disclosures

DAA is author of an UpToDate article on food allergy and a number of references cited in this topic. MHA is an author of a reference cited in this topic.

Peer reviewers

Robert Taylor, MBChB MRCP(UK) MRCP(London) DipMedTox DipTher PGDME FHEA FRCEM

Acute Hospital Sub Dean (Cornwall)

Honorary Clinical Senior Lecturer

Consultant Emergency Physician

The Knowledge Spa

Royal Cornwall Hospital

Truro

UK

Disclosures

RT declares that he has no competing interests.

Editors

Celia Pincus

Section Editor, BMJ Best Practice

Disclosures

CP declares that she has no competing interests.

Susan Mayor

Lead Section Editor, BMJ Best Practice

Disclosures

SM works as a freelance medical journalist and editor, video editorial director and presenter, and communications trainer. In this capacity, she has been paid, and continues to be paid, by a wide range of organisations for providing these skills on a professional basis. These include: NHS organisations, including the National Institute for Health and Care Excellence, NHS Choices, NHS Kidney Care, and others; publishers and medical education companies, including the BMJ Group, the Lancet group, Medscape, and others; professional organisations, including the British Thoracic Oncology Group, the European Society for Medical Oncology, the National Confidential Enquiry into Patient Outcome and Death, and others; charities and patients’ organisations, including the Roy Castle Lung Cancer Foundation and others; pharmaceutical companies, including Bayer, Boehringer Ingelheim, Novartis, and others; and communications agencies, including Publicis, Red Healthcare and others. She has no stock options or shares in any pharmaceutical or healthcare companies; however, she invests in a personal pension, which may invest in these types of companies. She is managing director of Susan Mayor Limited, the company name under which she provides medical writing and communications services.

Rachel Wheeler

Lead Section Editor, BMJ Best Practice

Disclosures

RW declares that she has no competing interests.

Julie Costello

Comorbidities Editor, BMJ Best Practice

Disclosures

JC declares that she has no competing interests.

Adam Mitchell

Drug Editor, BMJ Best Practice

Disclosures

AM declares that he has no competing interests.

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