Food Allergy

A food allergy is an immune system response to a food that the body mistakenly believes is harmful.

Once the immune system decides that a particular food is harmful, it creates specific antibodies to it. The next time the individual eats that food, the immune system releases massive amounts of chemicals, including histamine, to protect the body. These chemicals trigger a cascade of allergic symptoms that can affect the respiratory system, gastrointestinal tract, skin, and/or cardiovascular system.

Scientists estimate that more than 12 million Americans have food allergies. That’s one in 25, or 4 percent of the population. ^{[1] [2][3]} The incidence of food allergy is highest in young children – one in 17 among those under age 3.^{[4] [5] [6]}.

About 3 million children in the U.S. have food allergies.^{[7] [8] [9] [10]}

Food allergy is believed to be the leading cause of anaphylaxis outside the hospital setting, causing an estimated 50,000 emergency department visits each year in the U.S. ^[11]

Signs and Symptoms

Symptoms of a food allergy reaction typically appear within minutes to two hours after the person has eaten the food to which he or she is allergic and may include one or more of the following:

• a tingling sensation, itching, or a metallic taste in the mouth
• swelling of the mouth, tongue, and throat
• hives
• itchy rash or eczema
• vomiting
• diarrhea
• severe abdominal cramps
• sensation of warmth
• wheezing, repetitive coughing, or difficulty breathing
• drop in blood pressure
• loss of consciousness

Anaphylaxis

Anaphylaxis is a serious allergic reaction that is rapid in onset and may cause death. Life-threatening reactions may get worse over a period of several hours. In some reactions, the symptoms go away, only to return two to three hours later. This is called a “biphasic reaction.” Often these second-phase symptoms occur in the respiratory tract and may be more severe than the first-phase symptoms. Studies suggest that biphasic reactions occur in about 20 percent of anaphylactic reactions. ^[12]

Individuals who have asthma in addition to food allergies may be at increased risk for having a life-threatening anaphylactic reaction to food.

Causes

Eight foods account for 90 percent of all food-allergic reactions in the U.S.: milk, eggs, peanuts, tree nuts (e.g., walnuts, almonds, cashews, pistachios, pecans), wheat, soy, fish, and shellfish. ^[13]

Diagnosis

The skin prick test or a blood test, such as the RAST (or radioallergosorbent test), is commonly used to begin to determine if an allergy exists. (The RAST is sometimes called the CAP-RAST or ImmunoCap test.)

Although both tests are reliable, there are instances where one is better than the other. Many doctors use a RAST for young children or for patients who have eczema or other skin problems that would make it difficult to read the results of a prick skin test. The results of either test must be interpreted by a qualified physician, along with other information, such as a history of symptoms and sometimes a food challenge, to determine whether a food allergy exists. A RAST test requires a blood sample. The sample is sent to a medical laboratory, where tests are done with specific foods to determine whether the patient has IgE antibodies to that food. The results are usually received within one week. A skin prick test is usually less expensive and can be done in the doctor’s office. The doctor places a drop of the substance being tested on the patient’s forearm or back and pricks the skin with a needle, allowing a tiny amount to enter the skin. If the patient has IgE antibodies to the substance, a wheal (mosquito bite-like bump) will form at the site within about 15 minutes.

Treatment

There is no cure for food allergies. Strict avoidance of food allergens and early recognition and management of allergic reactions to food are important measures to prevent serious health consequences.

Food allergies are life-altering for everyone involved and require constant vigilance. ^{[14] [15] [16] [17]}

Reading ingredient labels for all foods is the key to avoiding a reaction. If a product doesn’t have a label, individuals with a food allergy should not eat that food. If you have any doubt whether a food is safe, call the manufacturer for more information. If one suspects an anaphylactic reaction is occurring, the following steps are typically recommended:

• Follow a physician's instructions for treatment, and administer medication promptly.
• Call Emergency Medical Services (or 911) and request an ambulance with epinephrine. Do not attempt to drive yourself to a medical facility. Get to a hospital as soon as possible and plan to stay at least four hours, in case symptoms return.

Medications

Epinephrine, also called adrenaline, is the medication of choice for treating an anaphylactic reaction. It works to reverse the symptoms and helps to prevent its progression. Epinephrine is available by prescription as a self-injectable device (EpiPen® or Twinject®).

Early administration of epinephrine is crucial to successfully treating anaphylactic reactions. ^[18]

Antihistamines (such as Benadryl®) and steroids (such as prednisone) are often used to help the recovery of a person with an anaphylactic reaction. Antihistamines and asthma medications (such as albuterol) may be administered with epinephrine, but never instead of epinephrine, because they cannot reverse many of the symptoms of anaphylaxis.

Research

Food allergy is a growing public health concern in the U.S. There is still much research to be done. Although not yet understood, the prevalence of food allergies and associated anaphylaxis appears to be on the rise. ^[19]

• Peanut allergy doubled in children over a five-year period (1997-2002). S^[20]
• Research suggests that food-related anaphylaxis might be underdiagnosed. ^[21]
• An increasing number of school students and staff have diagnosed life-threatening allergies. ^[22].
• A 2007 study has shown that milk allergy may persist longer in life than previously thought. Of 800 children with milk allergy, only 19 percent had outgrown their allergy by age 4, and only 79 percent had outgrown it by age 16. ^[23]

References

1. ↑ Centers for Disease Control and Prevention, National Center for Health Statistics. Health Data for All Ages. Allergic conditions among children: US, 2000-2005. Available online at: http://209.217.72.34/HDAA/TableViewer/tableView.aspx?ReportId=205
2. ↑ National Institute of Allergy and Infectious Diseases, National Institutes of Health. Report of the NIH Expert Panel on Food Allergy Research. March 13-14, 2006. Available online at: http://www3.niaid.nih.gov/topics/foodAllergy/ReportFoodAllergy.htm
3. ↑ U.S. Census Bureau. State and County QuickFacts. Available online at: http://quickfacts.census.gov/qfd/states/00000.html.
4. ↑ Sampson HA. Update on food allergy. J Allergy Clin Immunol. 2004 May;113(5):805-19.
5. ↑ Sampson HA. 9. Food allergy. J Allergy Clin Immunol. 2003 Feb;111(2 Suppl):S540-7.
6. ↑ U.S. Census Bureau. State and County QuickFacts. Available online at: http://quickfacts.census.gov/qfd/states/00000.html
7. ↑ Sampson HA. Update on food allergy. J Allergy Clin Immunol. 2004 May;113(5):805-19.
8. ↑ Sampson HA. 9. Food allergy. J Allergy Clin Immunol. 2003 Feb;111(2 Suppl):S540-7.
9. ↑ Centers for Disease Control and Prevention, National Center for Health Statistics. Health Data for All Ages. Allergic conditions among children: US, 2000-2005. Available online at: http://209.217.72.34/HDAA/TableViewer/tableView.aspx?ReportId=205.
10. ↑ U.S. Census Bureau. State and County QuickFacts. Available online at: http://quickfacts.census.gov/qfd/states/00000.html.
11. ↑ Decker, W., Campbell, R., Manivannan, V., Luke, A., St. Sauver, J., Weaver, A., et al. (2008). The etiology and incidence of anaphylaxis in Rochester, Minnesota: A report from the Rochester Epidemiology Project. The Journal of Allergy and Clinical Immunology. 122(6), 1161-1165
12. ↑ Sampson, H., Muñoz-Furlong, A., Campbell, R., Adkinson, N., Bock, S., Branum, A., et al. (2006). Second symposium on the definition and management of anaphylaxis: Summary report – Second National Institute of Allergy and Infections Disease/Food Allergy & Anaphylaxis Network symposium. Journal of Allergy and Clinical Immunology. 117(2), 391-397.
13. ↑ National Institute of Allergy and Infectious Diseases (July 2004). NIH Publication No. 04-5518: Food Allergy: An Overview
14. ↑ Sicherer SH, Noone SA, Muñoz-Furlong A. The impact of childhood food allergy on quality of life. Ann Allergy Asthma Immunol. 2001 Dec;87(6):461-4.
15. ↑ Bollinger ME, Dahlquist LM, Mudd K, Sonntag C, Dillinger L, McKenna K. The impact of food allergy on the daily activities of children and their families. Ann Allergy Asthma Immunol. 2006 Mar;96(3):415-21.
16. ↑ Marklund B, Ahlstedt S, Nordström G. Health-related quality of life among adolescents with allergy-like conditions - with emphasis on food hypersensitivity. Health Qual Life Outcomes. 2004 Nov 19;2:65.
17. ↑ Cohen BL, Noone S, Muñoz-Furlong A, Sicherer SH. Development of a questionnaire to measure quality of life in families with a child with food allergy. J Allergy Clin Immunol. 2004 Nov;114(5):1159-63.
18. ↑ Joint Task Force on Practice Parameters; American Academy of Allergy, Asthma and Immunology; American College of Allergy, Asthma and Immunology; Joint Council of Allergy, Asthma and Immunology. J Allergy Clin Immunol. 2005 Mar;115(3 Suppl 2):S483-523.
19. ↑ Joint Task Force on Practice Parameters; American Academy of Allergy, Asthma and Immunology; American College of Allergy, Asthma and Immunology; Joint Council of Allergy, Asthma and Immunology. J Allergy Clin Immunol. 2005 Mar;115(3 Suppl 2):S483-523.
20. ↑ icherer SH, Muñoz-Furlong A, and Sampson HA. Prevalence of peanut and tree nut allergy in the United States determined by means of a random digit dial telephone survey: A 5-year follow-up study. Journal of Allergy and Clinical Immunology 2003;112:1203-7.
21. ↑ Clark S, Bock SA, Gaeta TJ, Brenner BE, Cydulka RK, et al. Multicenter study of emergency department visits for food allergies. Journal of Allergy and Clinical Immunology 2004;113:347-52.
22. ↑ National Association of School Nurses. Epinephrine Use in Life-Threatening Emergencies (Position Statement). Adopted November, 2000, Revised June, 2005
23. ↑ Skripak JM, Matsui EC, Mudd K, Wood RA. The natural history of IgE-mediated cow's milk allergy. J Allergy Clin Immunol. 2007 Nov;120(5):1172-7.

External Links

• http://www.foodallergy.org
• http://www.aaaai.org
• http://www.acaai.org
• http://www.epipen.com/
• http://www.twinject.com/