Anaphylactic Reactions: The Most Severe Type of Allergic Reaction

Anaphylaxis is a severe allergic reaction and medical emergency involving the entire body. It requires immediate medical help. Symptoms include difficulty breathing, loss of consciousness, and even death if not treated promptly and properly.

How Anaphylactic Reactions Occur

An anaphylactic reaction is triggered the same way other, less severe allergic reactions are. The immune system overreacts to otherwise harmless substances. When this allergic reaction is severe, as in anaphylaxis, it affects the entire body. The skin, respiratory system, heart and lungs, eyes, uterus, and bladder may be involved. This whole-body allergic reaction may cause:


  • nausea
  • vomiting
  • abdominal cramps
  • hives
  • swelling of the lips
  • diarrhea
  • itchy skin
  • anxiety
  • headache
  • joint swelling
  • coughing, sneezing, wheezing
  • shortness of breath
  • itchy mouth and throat
  • nasal congestion
  • hoarseness
  • warmth and flushing
  • widespread, intense skin redness
  • uterine cramping
  • itchy, watery, swollen eyes
  • chest pain and tightness
  • difficulty breathing
  • low blood pressure
  • shock, loss of consciousness, and even death

If you have any of these symptoms after allergy testing or after exposure to an allergen, call 911 immediately.

If you think you've had an anaphylactic reaction, see an allergy specialist for follow-up evaluation and treatment. The allergy specialist can prescribe a medication called an epinephrine shot to carry with you and use if you begin to experience this severe form of allergic reaction in the future.


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Written by Karen Serrano, MD Emergency Medicine resident at the University of Wisconsin-Madison.

Reviewed by Lisa V. Suffian, MD

Instructor of Clinical Pediatrics in the Division of Allergy and Pulmonary Medicine at Saint Louis Children's Hospital, Washington University School of Medicine

Assistant Clinical Professor in the Department of Pediatrics at Cardinal Glennon Children's Hospital, Saint Louis University

Board certified in Allergy and Immunology

Last updated June 2008