Anaphylaxis

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Anaphylaxis

Definition

Anaphylaxis is a rapidly progressing, lifethreatening 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 and symptoms

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.

Diagnosis

Anaphylaxis is diagnosed based on the rapid development of symptoms in response to a suspected allergen. Identification of the cause may be done with RAST testing, a blood test that identifies IgE reactions to specific allergens. Skin testing can also be done, but with care. Food challenges should be avoided.

Sometimes, the offending allergen is not readily apparent, and the diagnosis of anaphylaxis could be overlooked. Also, some of the symptoms resemble other conditions such as cardiac arrhythmia, myocardial infarction, seizure disorder, insulin reaction, and pulmonary embolism.

A detailed medical history taken of the patient before medical or surgical procedures may help in diagnosis if symptoms manifest. Often, the only evidence of anaphylactic reaction is anecdotal or self-reported surveys.

Treatment

Emergency treatment of anaphylaxis involves injection of adrenaline (epinephrine), which constricts blood vessels and counteracts the effects of histamine. Oxygen may be given, as well as intravenous replacement fluids. Antihistamines may be used for skin rash, and aminophylline for bronchial constriction. If the upper airway is obstructed, the insertion of a breathing tube or tracheotomy tube may be needed.

Treatment should be administered immediately. Epinephrine injected directly into muscle tissue is quick and extremely effective. Intravenous injections require specific calculations regarding the dilution of adrenaline in order for it to be administered. Epinephrine inhalers are not as effective, as are short-acting b-agonist inhalers used by persons suffering from asthma. These can prove fatal because they delay effective treatment.

Self-administered epinephrine devices such as EpiPen and EpiE-Z are life-saving tools. Patients must be properly trained in their use and instructed to keep these devices updated and close at hand.

Patients should also be monitored for 24 hours after the symptoms have subsided. Symptoms have been known to return several hours later when the patient has returned home from the hospital.

Prognosis

The rapidity of symptom development is an indication of the likely severity of reaction: the faster symptoms develop, the more severe the ultimate reaction. Prompt emergency medical attention and close monitoring reduces the likelihood of death. Nonetheless, death is possible from severe anaphylaxis. For most people who receive rapid treatment, recovery is complete.

Health care team roles

All medical personnel should be trained to recognize the symptoms of anaphylaxis and to use the proper emergency procedures. Nurses and physicians assistants need to ask patients about their history of allergy when preparing them for a doctor's visit or before invasive procedures. Physicians, lab personnel, and nurses need to routinely ask whether a person is allergic to medications and latex. Inquiries about food allergies can be very helpful when preparing to administer vaccinations or medications. A patient's allergy history may have changed since the last doctor's visit. Even a small reaction like a rash on initial exposure to an allergen can be an indicator that a patient may have a more serious reaction on subsequent encounters with the agent.

In the case of latex allergy in the wake of a surgical procedure, medical personnel will need to strip the operating room or the procedure room of all latex items. Some patients are so sensitive to latex in any form that even inhaling a latex particle in the air could be life threatening.

Prevention

Avoidance of the allergic trigger is the only reliable method of preventing anaphylaxis. For insect allergies, this requires recognizing likely nest sites, wearing long sleeves, and using insect repellant. Preventing food allergies requires knowledge of the prepared foods or dishes in which the allergen is likely to occur, reading labels, and carefully questioning about ingredients when dining out. Use of a Medic-Alert tag detailing drug allergies is vital to prevent inadvertent administration during a medical emergency. In addition, patients with latex sensitivity need to avoid using latex products of all kinds and must notify medical and dental personnel of their latex allergy.

People prone to anaphylaxis should carry an Epipen or Ana-kit, which contains an adrenaline dose ready for injection. They also should be carefully trained in its use.

KEY TERMS

Allergen— A substance that causes an allergic reaction.

Adrenocorticotropic hormone (ACTH)— A hormone normally produced by the pituitary gland, sometimes taken as a treatment for arthritis and other disorders.

Antibody— An immune system protein that binds to a substance from the environment.

Histamine— A substance produced by the immune system in response to an allergen.

NSAIDs— Non-steroidal anti-inflammatory drugs, including aspirin and ibuprofen.

Tracheostomy tube— A tube that is inserted into an incision in the trachea (tracheotomy) to relieve upper airway obstruction.

Resources

BOOKS

Lawlor Jr., G.J., T.J. Fischer, and D.C. Adelman. Manual of Allergy and Immunology. Boston/New York/Toronto/London: Little, Brown and Co., 1995.

PERIODICALS

Davis, Blanca Rosa. "Perioperative Care of Patients with Latex Allergy." AORN Journal 72 no. 1 (July 2000): 47.

Jurewizc, Mary Ann. "Anaphylaxis: When the Body Overreacts." Nursing 30 no. 7 (July 2000): 58.

Neugut, Alfred I., Anita T. Ghatak, and Rachel L. Miller. "Anaphylaxis in the United States: An Investigation into Its Epidemiology." Archives of Internal Medicine 161 no. 1 (January 8, 2001): 15.

Socjerer, Scott H., Joel A. Forman, and Sally A. Noone. "Use Assessment of Self-Administered Epinephrine among Food-allergic Children and Pediatricians." Pediatrics 105 no. 2 (February 2000): 359.