Anaphylaxis (v1.2)

V1.2.4. March 27, 2023

Definition and Pathophysiology (3)

“Anaphylaxis is a severe, systemic hypersensitivity reaction that is rapid in onset and characterized by life-threatening airway, breathing, and/or circulatory problems, and that is usually associated with skin and mucosal changes” (3).

Pathophysiologic changes in anaphylaxis and mediators that have been implicated in these processes (3)

Diagnostic Criteria (2)

Clinical criteria for the diagnosis of anaphylaxis. Anaphylaxis is likely when 1 of 3 criteria are fulfilled: (1) acute onset of an illness (minutes to hours) with involvement of the skin, mucosal tissue, or both with either respiratory involvement or reduced blood pressure (BP)/associated symptom of end-organ dysfunction; or (2) ≥2 of the following that occur rapidly after exposure to a likely allergen for the patient, including (i) involvement of skin-mucosal tissue, (ii) respiratory involvement, (iii) reduced blood pressure or associated symptoms, or (iv) gastrointestinal symptoms; or (3) reduced blood pressure as a result of exposure to a known allergen trigger. 

Sensitivity and specificity of diagnostic criteria (1)

Proposed diagnostic criteria by the National Institute of Allergy and Infectious Diseases/Food Allergy and Anaphylaxis Network (NIAID/ FAAN)(2), are proposed to be useful to the emergency department:

Emergency anaphylaxis management algorithm (2)

Suggested key clinical advice (4)

Related Drugs


® 2023 EMDrugs. All rights reserved.


This website provides general information and discussion about medications, health, and related subjects. The words and other con­tent pro­vided in this website, and in any linked mate­ri­als, are not intended and should not be con­strued as med­ical advice. If the reader or any other per­son has a med­ical con­cern, he or she should con­sult with an appropriately-licensed physi­cian or other legally accredited health care worker in the country that resides or is visiting. 


Please do not delay your medical concerns and potential health emergencies by searching information in this website, instead look out for medical opinion in the services that exist with that specific purpose and work under the respective local health-care regulations. 


The views expressed on this blog and web­site have no rela­tion to those of any academic, hospital, practice or other insti­tu­tion with which the authors are  affiliated. 


For other instances, the authors of this website do not have any conflict of interest with any institution or pharmaceutical company in particular, and do not receive any compensation about any licenced drug mentioned in the website. In the same matter, the website is not intended to recommend any specific patented medication.

EMDrugs Team