Anaphylaxis is a potentially life-threatening allergic reaction to specific triggers such as foods, medications, insect venom, or latex. Although comprehensive information is not available, the best statistics indicate that as many as 40.9 million people in the United States suffer from severe allergies that may put them at risk for anaphylaxis—and the numbers are growing.^1-10,28 Anaphylactic symptoms may include difficulty breathing or swallowing, hives, or swelling around the mouth or eyes. Anaphylaxis may be successfully treated with epinephrine, but sufferers must be on alert for a secondary reaction occurring in the hours after the initial attack, called a biphasic reaction.

Definition

Anaphylaxis, or anaphylactic shock, is an allergic reaction that can be fatal within minutes, either through swelling that shuts off airways or through a dramatic drop in blood pressure.

Anaphylaxis occurs in individuals when they are exposed to an allergen to which they are allergic. An allergen is almost always a protein that is treated by the immune system as a foreign substance. Contact with, or ingestion of this allergen will set off a chain reaction in a person's immune system that may lead to swelling of the airways, loss of blood pressure, and loss of consciousness, resulting in anaphylactic shock.

The function of the immune system is to protect the body from foreign invaders.

Some anaphylactic reactions involve only one organ system, such as the respiratory tract or skin. However, in anaphylaxis, multiple systems are usually affected simultaneously. This includes the upper and lower respiratory tracts, cardiovascular system, and gastrointestinal tract.

The respiratory tract begins with the nose and ends with the lungs. It is responsible for bringing fresh oxygen into the blood and expelling the body's waste, carbon dioxide.

The cardiovascular system consists of the heart and many blood vessels called veins and arteries. This system pumps blood throughout the body, delivering fresh oxygen and removing waste products.

The gastrointestinaI tract extends from the mouth to the anus. It is responsible for receiving food, digesting it into nutrients, absorbing the nutrients into the bloodstream, and also eliminating waste products from the body.

In essence, the immune systems of individuals with allergies perceive allergens (e.g., food proteins, medications, insect venom, latex rubber) as foreign substances to which their bodies are primed or sensitized to react against. More specifically, the part of the immune system that is usually involved in fighting foreign organisms forms proteins called IgE antibodies that sit on the surface of specialized mast cells. Mast cells are filled with chemicals called mediators, such as histamines and leukotrienes, which are released when the allergenic protein reacts with the IgE antibody.

The release of these IgE mediators causes:

• Contraction of smooth muscle found in the respiratory and gastrointestinal tracts, which can produce wheezing and gastrointestinal symptoms (cramps, vomiting, nausea, or diarrhea)
• Vascular dilation that can cause swelling (angioedema), hives (urticaria), and a decrease in the fluid volume of blood that can lead to shock

Symptoms

The most distinctive symptoms of anaphylaxis include:

• Hives
• Swelling of the throat, lips, tongue, or around the eyes
• Difficulty breathing or swallowing

Other common symptoms of anaphylaxis may include:

• Metallic taste or itching in the mouth
• Generalized flushing, itching, or redness of the skin
• Abdominal cramps, nausea, vomiting, or diarrhea
• Increased heart rate
• Sudden decrease in blood pressure (and accompanying paleness)
• Sudden feeling of weakness
• Anxiety or an overwhelming sense of doom
• Collapse
• Loss of consciousness

Anaphylaxis Statistics

The number of people in the United States with allergic sensitivities that put them at risk for anaphylaxis may be as high as 40.9 million.²⁸ Actual incidence is unknown, but it is believed to be under-reported as anaphylaxis is often confused with asthma attacks and other respiratory emergencies.

The following statistics may help you to better understand who is affected by anaphylaxis and the importance of treating it with epinephrine.

At risk for anaphylaxis

• There are 1.3 million to 13 million people who are allergic to insect stings.^3,11
  • Each year, 40 to 400 anaphylactic deaths occur from insect stings.^1,11-13
  • In people who have had a reaction to an insect sting, 30% to 60% will have a repeat reaction that is as severe or more severe than the first episode.¹⁴
• Food allergies affect 5.4 million to 7 million people.²
  • The incidence of food allergy in children is increasing.⁶
  • More than 2 million, or 8%, of U.S. children under three years old have food allergies.¹⁶
  • There are three million, or 1.1%, Americans who are allergic to peanuts or tree nuts.²
  • Each year, 125 deaths are attributed to food-related anaphylaxis.¹⁷
• There are 2.7 million to 16 million people who are allergic to latex.^9,10,18
  • In health care workers, 8% to 17% are latex sensitive.^7,8,18
• Up to 27 million people, 0.7% to 10%, are allergic to penicillin.¹⁹
  • Penicillin is responsible for about 5,440 cases of fatal anaphylaxis per year, which accounts for an estimated 75% of U.S. anaphylaxis deaths.^1,20
  • Most deaths occur among individuals with no history of drug allergies.¹
• Asthmatics are at particular risk for experiencing anaphylaxis.¹

Incidence

• Anaphylaxis occurs at a rate of 21 per 100,000 people each year in the Northern United States²¹
  • Nearly 82,000 episodes of anaphylaxis may occur each year in the United States²²
  • More than 57,000 Americans may experience anaphylaxis each year.²²

Importance of carrying and using epinephrine

• In one study of children and adolescents, 10 out of 13 fatal or near fatal anaphylactic reactions occurred outside of the home.²³
• None of the fatalities had epinephrine with them; all of the non-fatalities received epinephrine before or within 5 minutes of developing severe symptoms.²³

Speed of potentially fatal anaphylaxis

• It takes only 1 to 2 minutes for a mild allergic reaction to escalate to anaphylaxis.²⁴
• The faster the onset of an anaphylactic reaction, the greater the likelihood that it will be severe.¹

 
Biphasic Reaction

As many as 25% of people who have an anaphylactic reaction will experience a recurrence in the hours following the beginning of the reaction and require further medical treatment, including additional epinephrine injections.^25-27 This delayed reaction is called biphasic, meaning two phases.

 
References

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2. Sicherer SH, Muñoz-Furlong A, Burke AW, et al. Prevalence of peanut and tree nut allergy in the US determined by a random digit dial telephone survey. J Allergy Clin Immunol. 1999;103:559-562.
    
3. Joint Task Force on Practice Parameters, American Academy of Allergy, Asthma and Immunology, American College of Allergy, Asthma & Immunology, and the Joint Council of Allergy, Asthma and Immunology. J Allergy Clin Immunol. The diagnosis and management of anaphylaxis. 1998;101(6 pt 2):S465-S528.
    
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18. Arellano R, Bradley J, Sussman G. Prevalence of latex sensitization among hospital physicians occupationally exposed to latex gloves. Anaesthesiology. 1992;77:905-908.
     
19. Boston Collaborative Drug Surveillance Program. Drug-induced anaphylaxis. JAMA. 1973;224:613.
     
20. Bochner BS, Lichtenstein LM. Anaphylaxis. N Engl J Med. 1991;324:1785.
     
21. Yocum MW, Butterfield JH, Klein JS, et al. Epidemiology of anaphylaxis in Olmstead County: a population-based study. J Allergy Clin Immun. 1999;104:452-457.
     
22. Weiler JM. Anaphylaxis in the general population: a frequent and occasionally fatal disorder that is under-recognized. J Allergy Clin Immunol. 1999;104:271-273.
     
23. Sampson H, Mendelson L, Rosen J. Fatal and near-fatal anaphylactic reactions to food in children and adolescents. N Engl J Med. 1992;327:380-384.
     
24. The Merck Manual. 16th ed. Merck Research Laboratories; 1992:331.
     
25. Stark BJ, Sullivan TJ. Biphasic and protracted anaphylaxis. J Allergy Clin Immunol. 1986;78:76.
     
26. Brazil E, MacNamara AF. "Not so immediate" hypersensitivity—the danger of biphasic anaphylactic reactions. J Accid Emerg Med. 1998;(4):252-253.
     
27. Korenblatt, et al. A retrospective study of the administration of epinephrine for anaphylaxis indicating need for more than one dose [abstract 234]. ACCP. 1998.
     
28. Neugut AI, Ghatak AT, Miller RL. Anaphylaxis in the United States: an investigation into its epidemiology. Arch Intern Med. 2001;161:15-21.