Anaphylaxis Emergency Guide | WhatAreAllergies.com
SJ

Medically reviewed by Dr. Sarah Jenkins, MD, FACAAI

Verified Reviewer

Board Certified Allergist & Immunologist · Clinical Allergy, Asthma & Immunology

Stanford University School of Medicine

Updated March 2026·Annual review cycle

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Allergy Reaction Severity Scale — Clinical Classification

Mild

Runny nose, sneezing

Moderate

Hives, nasal congestion, itchy eyes

Severe

Asthma flare, widespread hives, swelling

Anaphylaxis

Throat closure, hypotension, shock

⚠ Anaphylaxis = Medical Emergency. Administer epinephrine immediately. Call 911.

Clinical allergy severity classification adapted from WAO Anaphylaxis Guidelines 2024. Anaphylaxis is a medical emergency requiring immediate epinephrine administration.

Understanding Anaphylaxis

Anaphylaxis is a medical emergency that requires immediate treatment. It occurs when the immune system overreacts to an allergen, releasing a flood of chemicals that can cause you to go into shock. Blood pressure drops suddenly, and your airways narrow, blocking normal breathing.

Common triggers include certain foods (like peanuts, tree nuts, fish, shellfish, and milk), insect stings, medications, and latex. In some cases, the cause remains unknown (idiopathic anaphylaxis).

MEDICAL EMERGENCY

Call 911 Immediately — These Symptoms Signal Anaphylaxis

Call 911 immediately if you experience:

  • Throat tightening, difficulty swallowing, or voice changes
  • Wheezing, shortness of breath, or inability to speak in full sentences
  • Sudden drop in blood pressure — dizziness, fainting, or collapse
  • Rapid weak pulse combined with pale or bluish skin
  • Severe vomiting or diarrhea following allergen exposure
  • Swollen lips, tongue, or face — especially with respiratory symptoms
  • Feeling of "impending doom" — take this symptom seriously
Do not wait to see if symptoms improve. Administer epinephrine first, then call 911. Antihistamines alone will NOT treat anaphylaxis.

Recognizing the Symptoms

Symptoms usually appear within minutes of exposure to an allergen, but sometimes they can occur a half-hour or longer after exposure. Key signs include:

  • Skin reactions, including hives and itching, and flushed or pale skin
  • A feeling of warmth or a sudden feeling of being too warm
  • The feeling of a lump in your throat or difficulty swallowing
  • Nausea, vomiting, or diarrhea
  • Abdominal pain
  • A weak and rapid pulse
  • Runny nose and sneezing
  • Swollen tongue or lips
  • Wheezing or difficulty breathing
  • A sense that something is wrong, or a feeling of impending doom

Medical Emergency Protocol

Anaphylaxis Emergency Action Protocol

Follow these steps in order — do not delay any step:

1

Administer Epinephrine Auto-Injector

Do this first

Use an EpiPen or Auvi-Q immediately. Inject into the outer mid-thigh — through clothing is acceptable. Hold in place for 10 seconds.

2

Call 911

Immediately after step 1

Call emergency services immediately after administering epinephrine. State clearly: 'This person is having anaphylaxis.' Do not drive yourself to the hospital.

3

Position the Patient

While waiting for 911

Lay the person flat on their back. Raise their legs 12 inches if possible. If vomiting or breathing difficulty, allow them to sit up slightly or lie on their side.

4

Second Epinephrine Dose (if available)

5–15 minutes after first dose

If symptoms do not improve within 5–15 minutes and a second auto-injector is available, administer it in the opposite thigh.

5

Hospital Evaluation — Mandatory

Always required

Even if symptoms resolve after epinephrine, a biphasic reaction can occur 1–72 hours later. Emergency department evaluation is required after every anaphylactic episode.

Call 911 Now

Important: Antihistamines (Benadryl) do NOT treat anaphylaxis. Epinephrine is the only first-line treatment. Never substitute or delay epinephrine.

Symptom CategorySpecific SignsUrgency Level
RespiratoryShortness of breath, wheezing, throat tightnessCritical - Treat Immediately
CardiovascularPale/blue coloring, weak pulse, dizziness, passing outCritical - Treat Immediately
Skin/MucosalHives, swelling (lips/face), itchingHigh - Monitor Closely
GastrointestinalVomiting, severe cramps, diarrheaHigh - Monitor Closely
Preparedness checklist adapted from ACAAI and FARE anaphylaxis patient guidance 2024.

Prevention and Preparedness

The best way to prevent anaphylaxis is to avoid known allergens. If you have a history of severe allergic reactions, always carry two doses of prescribed epinephrine. Ensure that family, friends, and coworkers know how to recognize anaphylaxis and use the auto-injector.

Consider wearing a medical alert bracelet or necklace indicating your allergy to inform first responders in an emergency.

Frequently Asked Questions

What is anaphylaxis?
Anaphylaxis is a severe, potentially life-threatening allergic reaction that can occur within seconds or minutes of exposure to an allergen.
When should I use an epinephrine auto-injector?
Administer epinephrine immediately if you experience severe symptoms like difficulty breathing, throat swelling, or a drop in blood pressure after allergen exposure.
Can I use antihistamines instead of epinephrine?
No. Antihistamines do not reverse cardiovascular or respiratory symptoms of anaphylaxis. Epinephrine is the only first-line treatment.

About the Medical Team

SJ
Medical Review

Dr. Sarah Jenkins, MD, FACAAI

Board Certified Allergist & Immunologist

Clinical Allergy, Asthma & Immunology

Stanford University School of Medicine
MC
Written by

Dr. Michael Chen, MD, PhD

Clinical Immunologist & Researcher

Translational Immunology, Biologic Therapies

Johns Hopkins University

All contributors hold active board certification in allergy, immunology, or a related specialty. View full credentials →

Medical References & Citations

  1. 1
    guideline2006

    Sampson HA, et al. "Second symposium on the definition and management of anaphylaxis: Summary report" — Journal of Allergy and Clinical Immunology.

    View source
  2. 2
    database2025

    American College of Allergy, Asthma & Immunology (ACAAI) "Allergy Facts and Figures" — ACAAI Clinical Resources.

    View source
  3. 3
    review2025

    World Allergy Organization (WAO) "White Book on Allergy — 2025 Update" — World Allergy Organization.

    View source
  4. 4
    guideline2024

    National Institute of Allergy and Infectious Diseases (NIAID) "Clinical Guidelines for the Diagnosis and Management of Food Allergy" — National Institutes of Health.

    View source
  5. 5
    guideline2024

    Muraro A, et al. "EAACI food allergy and anaphylaxis guidelines: Diagnosis and management of food allergy" — Allergy — European Journal of Allergy and Clinical Immunology.

This content reflects clinical guidelines current as of the last review date shown above. Always consult a qualified healthcare provider for personalized medical advice.