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    Anaphylaxis (Severe Allergic Reaction)

    Introduction to anaphylaxis

    Anaphylaxis refers to a rapidly developing and serious allergic reaction that affects a number of different areas of the body at one time. Severe anaphylactic reactions can be fatal. Most people experience allergy symptoms only as a minor annoyance. However, a small number of people are susceptible to a reaction that can lead to shock or even death.
    Anaphylaxis is often triggered by substances that are injected or ingested and thereby gain access into the blood stream. An explosive reaction involving the skin, lungs, nose, throat, and gastrointestinal tract can then result. Although severe cases of anaphylaxis can occur within seconds or minutes of exposure and be fatal if untreated, many reactions are milder and can be ended with prompt medical therapy.


    Anaphylaxis is an acute systemic (whole body) type of allergic reaction which occurs when a person has become sensitized to a certain substance or allergen and is again exposed to the allergen. Some drugs, such as those used for pain relief or for X-rays, may cause an anaphylactoid reaction on first exposure. Histamines and other substances released into the bloodstream cause blood vessels to dilate and tissues to swell. Anaphylaxis may be life-threatening if obstruction of the airway occurs, if blood pressure drops, or if heart arrhythmias occur.
    What does anaphylaxis mean?
    To fully understand this term, we need to go back almost 100 years. The story begins on a cruise aboard Prince Albert I of Monaco's yacht. The Prince had invited two Parisian scientists to perform studies on the toxin produced by the tentacles of a local jellyfish, the Portuguese Man of War. Charles Richet and Paul Portier were able to isolate the toxin and tried to vaccinate dogs in the hope of obtaining protection, or "prophylaxis," against the toxin. They were horrified to find that subsequent very small doses of the toxin unexpectedly resulted in a new dramatic illness that involved the rapid onset of breathing difficulty and resulted in death within 30 minutes.

    Richet and Portier termed this "anaphylaxis" or "against protection." They rightly concluded that the immune system first becomes sensitized to the allergen over several weeks and upon re-exposure to the same allergen may result in a severe reaction. An allergen is a substance that is foreign to the body and can cause an allergic reaction in certain people.
    Allergy Facts
    The first documented case of presumed anaphylaxis occurred in 2641 B.C. when Menes, an Egyptian pharaoh, died mysteriously following a wasp or hornet sting. Later, in Babylonian times, there are two distinct references to deaths due to wasp stings.
    Charles Richet was awarded the Nobel Prize in 1913 for his work on anaphylaxis.
    Richet went on to suggest that the allergen must result in the production of a substance, which then sensitized the dogs to react in such a way upon re-exposure. This substance turned out to be IgE.

    In the first part of the 20th century, anaphylactic reactions were most commonly caused by tetanus diphtheria vaccinations made from horse serum. Today, human serum is used for tetanus prevention, and the most common causes of anaphylaxis are now penicillin and other antibiotics, insect stings, and certain foods.

    What are common causes of anaphylaxis?

    The causes of anaphylaxis are divided into two major groups:

    IgE mediated: This form is the true anaphylaxis that requires an initial sensitizing exposure, 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 re-exposure.

    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. You may not remember an uneventful sting or be aware of "hidden" allergens in foods.


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    Last edited by trimurtulu; 02-25-2009 at 01:07 PM.

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