• Reviewed on 7/12
    By Dr. Alam

    • Rafeul Alam, MD

      Rafeul Alam, MD, PhD  
      Dept. of Medicine
      Chief, Division of Allergy & Clinical Immunology

      View full profile

Anaphylaxis: Overview

Anaphylaxis is a systemic (whole body), life-threatening allergic reaction, and is the most severe type of allergic reaction. Fortunately, it is very rare and many people with allergies will not experience anaphylaxis.

Anaphylaxis can be caused by allergies to many environmental agents. The common ones are:

In addition to allergens, physical exertion can cause anaphylaxis. This is known as exercise-induced anaphylaxis. Some forms of anaphylaxis are called idiopathic (unknown cause). Doctors diagnose this condition when they rule out the contribution from environmental factors.



Symptoms of anaphylaxis often appear quickly. They often appear within minutes of exposure to an allergen (a substance which causes an allergic reaction). In a few cases, reactions have been delayed as much as 12 to 24 hours. Symptoms of anaphylaxis include:

  • Breathing difficulties, coughing, chest tightness or wheezing

  • Dizziness, fainting, rapid or weak heartbeat

  • Swelling in the mouth and throat or trouble swallowing

  • Flushing, itching, hives or a feeling of warmth

  • Vomiting, diarrhea or stomach cramping along with some of the symptoms mentioned above


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