Anaphylaxis Health Article

Definition

Anaphylaxis is a rapidly progressing, life-threatening allergic reaction.

Description

Anaphylaxis is a type of allergic reaction, in which the immune system responds to otherwise harmless substances from the environment. Unlike other allergic reactions, however, anaphylaxis can result in death. Reaction may begin within minutes or even seconds of exposure, and rapidly progress to cause airway constriction, skin and intestinal irritation, and altered heart rhythms. In severe cases, it can result in complete airway obstruction, shock, and death.

In 2001, more cases of anaphylaxis have been reported, especially in reaction to latex and exotic food antigens. The increased use of latex gloves in hospitals, doctors' offices, dentist offices, and among forensic investigators has also increased exposure to latex allergens.

The broadening of the Western diet, with the incorporation of more exotic foods and increased food processing, also exposes more people to possible food allergens, and at earlier ages. Peanut oil, for example, is often used in fast-food restaurants, and sulfites are used in processed meats and seafood. There is still no labeling for trace amounts of foods or food additives. Unfortunately, problem food allergens can still be present in favorite foods, even if the label does not show it. In some cases, even a small amount can prove fatal in certain individuals.

Causes

Like the majority of other allergic reactions, anaphylaxis is caused by the release of histamine and other chemicals from mast cells, which are a type of white blood cell found in large numbers in the tissues that regulate exchange with the environment: the airways, digestive system, and skin.

On their surfaces, mast cells display antibodies called immunoglobulin type E (IgE). These antibodies are designed to detect environmental substances to which the immune system is sensitive. Substances from a genuinely threatening source such as bacteria or viruses are called antigens. A substance that most people tolerate well, but to which others have an allergic response, is called an allergen. When IgE antibodies bind with allergens, they cause the mast cells to release histamine and other chemicals that spill out onto neighboring cells.

The interaction of these chemicals with receptors on the surface of blood vessels causes the vessels to leak fluid into surrounding tissues, resulting in fluid accumulation, redness, and swelling. On the smooth muscle cells of the airways and digestive system, they cause constriction. On nerve endings, they increase sensitivity and cause itching.

In anaphylaxis, the dramatic response is due both to extreme hypersensitivity to the allergen and its usually systemic distribution. Allergens are more likely to cause anaphylaxis if they are introduced directly into the circulatory system by injection. However, exposure by ingestion, inhalation, or skin contact can also cause anaphylaxis. In some cases, anaphylaxis may develop over time from less severe allergies.

Anaphylaxis most often results from allergens in foods, drugs, latex, and insect venom. Specific causes include, but are not limited to:

• fish, shellfish, and mollusks
• peanuts, tree nuts, and seeds
• eggs
• milk
• insulin in vegetables and processed foods
• stings of bees, wasps, and hornets
• preservatives, especially sulfites and parabens
• vaccines (e.g. flu, measles, rabies, chicken pox, and diphtheria-tetanus-pertussis) prepared with a gelatin base made from pork products
• antibiotics, including penicillin and its derivatives, cephalosporins, streptomycin, tetracycline, and sulphonamides
• gamma globulin and human serum albumin
• hormones like insulin, ACTH, and glucocorticoids
• anti-inflammatory drugs such as aspirin, ibuprofen, and other NSAIDs
• anti-venoms
• antiseptics such as mercurochrome
• allergy immunotherapy vaccines
• radiopaque dyes used in diagnostic studies (radiocontrast media)
• latex from exam gloves, catheters, tubing, condoms, etc.
• local anesthetics
• dyes (erythrosine and resorcinol, used in hair dyes)

Exposure to cold or exercise can also trigger anaphylaxis in some individuals.

Symptoms

Symptoms may include:

• flushing of face, head, or hands
• urticaria (hives)
• swelling and irritation of the tongue or mouth
• swelling of the sinuses
• difficulty breathing
• wheezing
• cramping, vomiting, or diarrhea
• anxiety or confusion
• strong, very rapid heartbeat (palpitations)
• drop in blood pressure
• chest pain
• loss of consciousness

Not all symptoms may be present, and some may be more severe than others. Symptoms usually occur immediately or within 20 minutes of exposure. On occasion, with food anaphylaxis, symptoms may not appear for several minutes or even hours. As a general guideline, the slower the onset of symptoms comes on, the less serious the episode. Symptoms may also reappear several hours later, sometimes in a more severe form.