Anaphylaxis

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What is Anaphylaxis?

Anaphylaxis is a sudden, severe allergic reaction to a substance (called an allergen) that can be life-threatening. Common substances which can cause as severe allergic reaction include bee stings, insect bites, peanuts, eggs, drugs given to the body, etc. Anaphylaxis suddenly affects the whole body, with severe allergic symptoms including: difficulty breathing, rash, swelling, tummy pain, and reduced blood pressure leading to shock. Anaphylaxis is a medical emergency where immediate treatment is needed to prevent potential death. When exposed to a foreign substance, some people suffer reactions identical to anaphylaxis, but in which no allergy is involved. These reactions are called anaphylactoid, meaning anaphylaxis-like reactions. In anaphylaxis, the immune system must be "primed" by previous allergen exposure. But in anaphylactoid reactions can occur with no previous allergen exposure at all. An example of something that can bring on a severe allergic reaction is radiographic contrast material (the dye injected into arteries and veins to make them show up on an x-ray). Although the mechanism of an anaphylactoid reaction is different. The allergy treatment is the same.

Who gets Anaphylaxis?

Anaphylaxis occurs infrequently. However, it is life-threatening and can occur at any time. Milder forms of anaphylaxis occur much more frequently than fatal anaphylaxis. The frequency of anaphylaxis is increasing and this has been attributed to the increasing number of potential allergens to which people are exposed. In the US, anaphylaxis causes approximately 500-1000 deaths in a year. However the figure is difficult to determine accurately because of underdiagnosis and underreporting. No major differences have been reported in the incidence and prevalence of severe allergic reactions between men and women. Anaphylaxis occurs in all age groups. While prior exposure to allergens is essential for the development of true anaphylaxis, severe allergic reactions occur even when no documented prior exposure exists. Thus, patients may react to a first exposure to an antibiotic or insect sting. Adults are exposed to more potential allergens than are pediatric patients. The elderly have the greatest risk of mortality from severe allergic reactions due to the presence of other diseases usually suffered by elderly population.

Predisposing Factors

The likelihood of an individual having anaphylaxis is influenced by the following:

age

gender

atopy (genetic tendency to develop classic allergic diseases)

route of exposure

history of prior exposure

history of prior anaphylactic episodes Other risks include prior history of any type of allergic reaction. After an initial exposure to a substance like bee sting toxin, the person's immune system becomes sensitized to that allergen. On a subsequent exposure, an allergic reaction occurs. Severe allergic reactions are usually triggered by a limited number of allergic exposures. These include injection, swallowing, inhaling or skin contact with an allergen by a severely allergic individual. Examples of injected allergens are bee, hornet, wasp and yellow jacket stings; certain vaccines which have been prepared on an egg medium; and allergen extracts used for diagnosis and treatment of allergic conditions. Antibiotics such as penicillin can trigger a reaction by injection or swallowing. Typically, a severe reaction caused by a food allergy occurs after eating that particular food, even a small bite. Allergy to peanuts is an example. Skin contact with the food rarely causes anaphylaxis. Foods most commonly associated with anaphylaxis are peanuts, seafood, nuts and, in children particularly, eggs and cow's milk. A severe allergic reaction from an inhaled allergen is rare. An increasingly recognizable example is when an allergic individual inhales particles from rubber gloves or other latex products.

Progression

The signs and symptoms of anaphylaxis may occur almost immediately after exposure or within the first 20 minutes after exposure. Rapid onset and development of potentially life threatening symptoms are characteristic markers of anaphylaxis.