Food Allergy

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Food Allergy

Allergy
Author Credentials 

Glen Porter, MD 
American Academy of Otolaryngic Allergy


Michael Platt, MD
American Academy of Otolaryngic Allergy

Module Summary

Food allergy is a common and growing problem in the US.  The spectrum of food allergy encompasses a wide variety of reactions to ingestion of foods that can cause IgE or non-Ige mediated reactions.  The clinical presentation can range from mild to life-threatening, and often includes a variety of organ systems including the skin, airways, and gastrointestinal tract.  The most common food allergens include milk, soy, egg, nuts (tree and peanut), shellfish, fish, and wheat.  Children with food allergies often outgrow them whereas adults are less likely to do so.  The particular food allergen also is less likely to be outgrown if it is a nut or shellfish allergen.  Diagnosis of food allergy is dependent on history of reactions after food ingestion, in conjunction with in vitro and skin testing to determine sensitizations.  The gold standard for allergy diagnosis is a food challenge to determine if a particular food elicits an allergic reaction upon ingestion.  The decision for diagnosis based on history alone, testing, or food challenge depends on the clinical scenario.  The mainstay of food allergy treatment is avoidance, although research is being conducted on desensitization protocols for various allergens.  When reactions do occur, mild reactions can be treated with medications for symptomatic relief (antihistamines, corticosteroids) whereas severe reactions including anaphylaxis require epinephrine administration and emergent care.  Patients with a severe food allergy should have epinephrine autoinjectors available for treatment of anaphylaxis in the case of accidental exposure.  

Module Learning Objectives 
  1. Explain the spectrum of IgE-mediated food allergies and the difference between intolerance and food allergy.
  2. Recognize the diagnostic work-up for food allergies.
  3. Cite treatments for food allergy.

 

Pathogenesis
  1. Explain the mechanism for IgE-mediated food allergy. 
  2. Describe that a food allergy is a rapid, reproducible reaction to small amounts of foods that can be severe including anaphylaxis.  
  3. Differentiate non-IgE mediated food allergy and intolerances from IgE-mediated food allergy.
  4. Discuss the natural history of food allergies: which are more likely to obtain tolerance, which are more likely to be lifelong.  Factors suggestive for developing tolerance is the degree of allergy, the severity of symptoms, and the type of food.

 

References: 

  1. Boyce JA et al. Guidelines for the diagnosis and management of food allergy in the United States: report of the NIAID-sponsored expert panel. NIAID-Sponsored Expert Panel, J Allergy Clin Immunol. 2010 Dec;126(6 Suppl):S1-58.

 

 

Incidence
  1. Cite the incidence of food allergy in the US: 5-7% of young children, 2-3% of adults, 11-15 million people in the USA
  2. Recognize the difference between food intolerance and food allergy.

 

References:

  1. Umasunthar T, et al. Incidence of food anaphylaxis in people with food allergy: a systematic review and meta-analysis. Clin Exp Allergy. 2015 Nov;45(11):1621-36

 

Genetics
  1. Explain the risk factors for food allergy: gender, family history, other atopic diseases, and vitamin D deficiency.
  2. Review the LEAP study where infants who avoided peanut had higher risks of developing peanut allergy. 

 

References:

  1. Du Toit G,et al. Randomized trial of peanut consumption in infants at risk for peanut allergy. N Engl J Med. 2015 Feb 26;372(9):803-13

 

Patient Evaluation
  1. Recognize that history is the most important factor in evaluation of food allergy. Symptoms of food allergy include hives, anaphylaxis, GI irritation, itching, swelling, angioedema, vomiting, wheezing, shortness of breath, nausea.

 

References:

  1. Sicherer SH, Sampson HA. Food allergy: A review and update on epidemiology, pathogenesis, diagnosis, prevention, and management. J Allergy Clin Immunol. 2018 Jan;141(1):41-58
Testing
  1. List the various testing methods for food allergy: skin prick testing, in vitro testing, and oral challenge.  
  2. Explain the high negative predictive value and the low positive predictive values of testing for food allergy. Widespread screening or ‘shotgun’ testing for foods leads to inappropriate avoidance due to false positives. Oral food challenge is the gold standard for diagnosis of food challenge.  
  3. Recognize component testing for foods that can add information about the severity and nature of the food allergy.

 

References:

  1. Boyce JA et al. Guidelines for the diagnosis and management of food allergy in the United States: report of the NIAID-sponsored expert panel. NIAID-Sponsored Expert Panel, J Allergy Clin Immunol. 2010 Dec;126(6 Suppl):S1-58

 

 

Treatment
  1. Recognize that avoidance is the mainstay of food allergy.  Counseling for reading labels, avoidance of foods without labels, alert bracelets, and epinephrine autoinjector is needed.
  • Patients with severe food allergies need to be educated in and prescribed epinephrine autoinjectors.  

 

References:

  1. Boyce JA et al. Guidelines for the diagnosis and management of food allergy in the United States: report of the NIAID-sponsored expert panel. NIAID-Sponsored Expert Panel, J Allergy Clin Immunol. 2010 Dec;126(6 Suppl):S1-58.

 

 

Case Studies
  1. A 10-year-old boy develops hives after eating peanuts. In vitro testing is highly positive for allergy to peanut.  He is instructed to avoid peanuts.
  2. A 12-year-old boy had vomiting after eating a peanut cake at a party.  He had in vitro testing with his PCP for 12 foods which was positive for four foods: strawberry, egg, milk, and almond, all of which he eats routinely without any symptoms.  Open food challenge in the office for the four positive foods and peanut reveals that he can tolerate all of these foods.  He does not need dietary avoidance.

 

Review Questions
  1. What is the treatment for food allergy?
  2. When do you do test patients for food allergy?
  3. Which patients with food allergy should be prescribed an epinephrine autoinjector?

 

Resources 

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  1. Annual Meeting Webcast (AMW):