What is anaphylaxis?

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    Last Updated: April 23, 2025

    Anaphylaxis is a rapid and potentially fatal allergic reaction that requires immediate treatment with epinephrine because it can be triggered by food allergies and results in various symptoms that affect the gastrointestinal, skin, respiratory, and cardiovascular systems. Symptoms can develop quickly and may not be immediately recognizable, so at-risk individuals should always have access to self-injectable epinephrine and seek emergency care if anaphylaxis is suspected.

    Anaphylaxis is a life-threatening allergic reaction that is rapid in onset and potentially fatal without prompt treatment with epinephrine. Food is the leading cause of anaphylaxis,[1] and anyone with an IgE-mediated food allergy can have an anaphylactic reaction. Common signs and symptoms include gastrointestinal manifestations (e.g., nausea, abdominal pain, vomiting, and diarrhea), skin reactions (e.g., itching, flushing), respiratory changes (e.g., nasal congestion, cough, wheezing, shortness of breath, sense of choking), and cardiovascular complications (e.g., hypotension, cardiovascular collapse).[2][3]

    Initial symptoms usually appear within minutes following exposure to the allergen, but it is not always immediately obvious that anaphylaxis is occurring because symptoms can evolve over time. Moreover, the severity of a previous reaction does not predict the severity of future reactions. As such, if anaphylaxis is suspected, it is recommended to administer intramuscular epinephrine as quickly as possible and seek emergency medical care because symptoms can come back (called biphasic anaphylaxis).[4] All people who have experienced or are at risk for anaphylaxis should have access to self-injectable epinephrine at all times.[5]

    What is anaphylaxis? - Examine