The definition of anaphylaxis is a systemic immediate hypersensitivity reaction caused by a rapid, IgE-mediated immune release of mediators from tissue mast cells and peripheral blood basophils.¹ The classic symptoms of anaphylaxis include hives, swelling around the eyes or mouth, and difficulty breathing or swallowing. Anaphylaxis is a health threat to nearly 40.9 million Americans every year,²⁸ and you may be surprised at the statistics associated with this condition.

 
Definition

Anaphylaxis, or anaphylactic shock, is a systemic 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 allergic individuals when they are exposed to an allergen to which they are allergic—this 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. Some anaphylactic reactions involve only one organ system, such as the respiratory tract or skin. However, in anaphylaxis, several systems are usually affected simultaneously, including the upper and lower respiratory tracts, cardiovascular system, and gastrointestinal tract.

In essence, the immune systems of allergic individuals perceive an allergen (eg, food proteins, medications, insect venom, latex rubber) as a foreign substance 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. These cells are filled with chemicals called mediators, such as histamines and leukotrienes, which are released when the allergenic protein reacts with the IgE. The release of these IgE mediators causes smooth-muscle contraction, which can produce wheezing and gastrointestinal symptoms, and vascular dilation that can cause angioedema, urticaria, and a decrease in plasma volume that can lead to shock.

Fortunately, effective treatment is available, so death from anaphylaxis can be prevented in most cases. Still, needless deaths occur every day because the symptoms of anaphylaxis go unrecognized or because treatment is not prompt enough.

 
Symptoms

The most distinctive symptoms of anaphylaxis are:

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

Other common symptoms 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
• Plunging blood pressure (and accompanying paleness)
• Sudden feeling of weakness
• Anxiety or an overwhelming sense of doom
• Collapse
• Loss of consciousness

 
Anaphylaxis Statistics

Risk and incidence of anaphylactic reactions
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.^1-10,28 Actual incidence is unknown, but it is believed to be underreported as anaphylaxis is often confused with asthma attacks and other respiratory emergencies.

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 US children under 3 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 US 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 States.²¹
  • Nearly 82,000 episodes of anaphylaxis may occur each year in the United States.²²
  • 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 nonfatalities 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

References

1. AAAAI. Anaphylaxis in schools and other child-care settings. Position statement #34. J Allergy Clin Immunol. 1998;102:173-176.
    
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. The diagnosis and management of anaphylaxis. J Allergy Clin Immunol. 1998;101(6 pt 2):S465-S528.
    
4. Kagy L, Blaiss MS. Anaphylaxis in children. Pediatric Annals. 1998;27:727-734.
    
5. Shehadi WH. Adverse reactions to intravascularly administered contrast media: a comprehensive study based on a prospective survey. Am J Roentgenol Radium Ther Nucl Med. 1975;124:145-152.
    
6. Katayama H, Yamaguchi K, Kozuka T, Takashima T, Seez P, Matsuura K. Adverse reactions to ionic and nonionic contrast media. A report from the Japanese Committee on the Safety of Contrast Media. Radiology. 1990;175:621-628.
    
7. Watts DN, Jacobs RR, Forrester B, et al. An evaluation of the prevalence of latex sensitivity among atopic and non-atopic intensive care workers. Am J Intern Med. 1998;34:359-363.
    
8. Liss GM, Sussman GL, Deal K, et al. Latex allergy: epidemiological study of 1351 hospital workers. Occup Environ Med. 1997;54:335.
    
9. Ownby DR, Ownby HE, McCullough J, Shafer AW. The prevalence of anti-latex IgE antibodies in 1000 volunteer blood donors. J Allergy Clin Immunol. 1996;97:1188-1192.
    
10. Kelly KJ, Sussman G, Fink JN. Stop the sensitization. J Allergy Clin Immunol. 1996;98:857-858.
     
11. Valentine MD. Anaphylaxis and stinging insect hypersensitivity. JAMA. 1992;268:2830-2833.
     
12. Lieberman P. Preventing fatalities from anaphylaxis: an allergist-immunologist's perspective. Allergy Proceedings. 1995;3:109-111.
     
13. Wyatt R. Anaphylaxis: how to recognize, treat and prevent potentially fatal attacks. Postgrad Med. 1996;100:87-99.
     
14. Reisman RE. Natural history of insect sting allergy: relationship of severity of symptomatic initial sting anaphylaxis to re-sting reactions. J Allergy Clin Immunol. 1992;30:335-339.
     
15. Sampson HA. Food allergy: primer on allergic and immunologic diseases. JAMA. 1997;288:1888-1894.
     
16. Bock SA. Prospective appraisal of complaints of adverse reactions to foods in children during the first 3 years of life. Pediatrics. 1987;79:683-688.
     
17. Burks AW, Sampson HA. Anaphylaxis and food allergy. In: DD Metcalf, HA Sampson, RA Simon, eds. Food Allergy: Adverse Reactions to Foods and Food Additives. 2nd ed. Malden, Mass: Blackwell Science; 1997.
     
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.