Anaphylaxis (Severe Allergic Reaction)

  • Medical Author:
    Jerry R. Balentine, DO, FACEP

    Dr. Balentine received his undergraduate degree from McDaniel College in Westminster, Maryland. He attended medical school at the Philadelphia College of Osteopathic Medicine graduating in1983. He completed his internship at St. Joseph's Hospital in Philadelphia and his Emergency Medicine residency at Lincoln Medical and Mental Health Center in the Bronx, where he served as chief resident.

  • Medical Editor: Melissa Conrad Stöppler, MD
    Melissa Conrad Stöppler, MD

    Melissa Conrad Stöppler, MD

    Melissa Conrad Stöppler, MD, is a U.S. board-certified Anatomic Pathologist with subspecialty training in the fields of Experimental and Molecular Pathology. Dr. Stöppler's educational background includes a BA with Highest Distinction from the University of Virginia and an MD from the University of North Carolina. She completed residency training in Anatomic Pathology at Georgetown University followed by subspecialty fellowship training in molecular diagnostics and experimental pathology.

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What are common causes of anaphylaxis?

Although anaphylaxis can be due to different causes, there are four major subtypes of anaphylaxis (reactions to food, drugs, latex, and insect stings).

The causes of anaphylaxis are divided into two major groups:

  • IgE mediated: This form is the true anaphylaxis that requires an initial sensitizing exposure (for example, an exposure to the substance that will later trigger the anaphylaxis) and occurs on a subsequent exposure. It involves the coating of mast cells and basophils (cells in the blood and tissue that secrete the substances that cause allergic reactions, known as mediators) by IgE, and the explosive release of chemical mediators upon reexposure.
  • Non-IgE mediated: These reactions, the so called "anaphylactoid" reactions, are similar to those of true anaphylaxis but do not require an IgE immune reaction. They are usually caused by the direct stimulation of the mast cells and basophils. The same mediators as occur with true anaphylaxis are released and the same effects are produced. This reaction can happen, and often does, on initial as well as subsequent exposures, since no sensitization is required.

The terms anaphylaxis and anaphylactoid (meaning "like anaphylaxis") are both used to describe this severe allergic reaction. Anaphylaxis is used to describe reactions that are initiated by IgE and anaphylactoid is used in reference to reactions that are not caused by IgE. The effects of the reactions are the same, however, and are generally treated in the same manner. Often, they can not be distinguished initially.

Although it may appear that IgE mediated anaphylaxis occurs upon a first exposure to a food, drug, or insect sting, there must have been a prior, and probably unwitting, sensitization from a previous exposure. One may not remember an uneventful sting or be aware of "hidden" allergens in foods.

Medically Reviewed by a Doctor on 6/24/2015

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