Indications for Testing

• Medical history (pruritus, urticaria, gastrointestinal symptoms, angioedema anaphylaxis) indicating temporal association between food ingestion and symptoms (<2 hours), chronic diarrhea and failure to thrive in children

Laboratory Testing

• Two tests
  • Skin testing (pin prick) is no longer necessary, although generally less costly
  • Specific food serum IgE testing along with appropriate history – group or panel allergen tests may be helpful (ImmunoCAP^® appears to be best validated)
  • Neither test predicts severity of allergic reaction
  • Positive results may not be diagnostic – cross reactivity exists between proteins
  • Serum tryptase – elevated at 1-4 hours after anaphylaxis and can help confirm diagnosis
• Food testing
  • Food challenges may be helpful but should not precede IgE testing
    • Administration of suspected food in gradually increasing doses
    • May be necessary if pin prick or IgE testing is negative and strong suspicion still exists for allergy 
    • May be dangerous to do food testing in certain patients with severe allergies
    • Needs to be performed under controlled circumstances with very specific endpoints
      • Double-blind testing – considered gold standard
• Patch testing – typically used in non-IgE mediated food allergy (eg, eosinophilic esophagitis)
  • No standard reagent methods or interpretation available
  • Not recommended by the National Institute of Allergy and Infectious Diseases for routine evaluation

Differential Diagnosis

• Carcinoid syndrome
• Celiac disease
• Giardia duodenalis
• Gustatory rhinitis
• Inflammatory bowel disease
• Lactase deficiency
• Scombroid poisoning – most cases from tuna, mahi-mahi and swiss cheese
• Sulfate ingestion

Food allergies are a common form of allergic presentation in childhood. The National Institute of Allergy and Infectious Diseases defines food allergy as an adverse immune response occurring reproducibly on exposure to a given food and is distinct from other adverse responses to food, such as food intolerance, pharmacologic reactions, and toxin-induced reactions.

Epidemiology

• Incidence
  • Varies by geographic region
  • Increased incidence reported over the past 10 years (especially peanut allergies)
• Age
  • Adults – <3% with allergies
  • Usually in children
    • Up to 6% of children <3 years are affected
• Sex
  • M:F, equal

Risk Factors

• History of asthma
• Parent or sibling with a history of atopy or asthma

Pathophysiology

• Any food can potentially sensitize the immune system and cause antibody production
  • Foods most likely to cause sensitivity include those that are
    • Water soluble
    • Heat resistant
    • Acidic
    • Proteolytic
• Most food allergies are IgE mediated but may also be IgG mediated
  • 90% of IgE-mediated allergies are caused by just eight foods – cow milk, soy, chicken eggs, peanuts, tree nuts, wheat, fish, and crustaceans
  • Non-IgE-mediated reactions are also common to soy, wheat, and cow milk
• Wheat, milk, egg and soy allergies usually disappear gradually with age
• Food intolerance is not the same as food allergy

Clinical Presentation

• Classic IgE-mediated (immediate hypersensitivity)
  • Reaction occurs within an hour after food is ingested
  • Classification
    • Oral allergy syndrome – pruritus, tingling, swelling of lips and palate after fresh fruit/vegetable 
      • Birch sensitivity – symptoms with raw carrots, celery and apples
      • Ragweed sensitivity – symptoms with cantaloupe, watermelon, honeydew and bananas
      • No symptoms when food is cooked
    • Gastrointestinal – nausea, abdominal pain, cramps, vomiting, diarrhea
    • Cutaneous – urticaria, angioedema, generalized pruritus, flushing, morbilliform rash
    • Respiratory – pruritus, tearing, nasal congestion, rhinorrhea, throat tightness, hoarseness, shortness of breath, dyspnea, wheezing
    • Cardiovascular – syncope, chest pain, dysrhythmia, hypotension, shock
    • Neurologic – anxiety, headache, seizure, loss of consciousness
  • Mixed IgE/non-IgE
    • Occurs 1-24 hours after food is ingested
    • Classification
      • Atopic dermatitis
      • Eosinophilic esophagitis/gastroenteritis
  • Non-IgE (cell-mediated)
    • Occurs 24 hours after food ingested
    • 80-85% of children outgrow food allergies by 5 years
    • Most persistent allergens are nuts, seeds, fish
  • Classification
    • Food protein-induced proctocolitis
      • Infants appear healthy
      • Blood-tinged stools in first 2-4 months of life
      • Usually secondary to milk or soy protein and most often in breast-fed infants
    • Food protein-induced enterocolitis syndrome
      • Infants appear ill
      • Bloody diarrhea, recurrent vomiting, failure to thrive
      • Most often secondary to milk and soy protein; rice, oat, other cereal grains, and chicken have also been implicated
      • Infants usually tolerate breast milk

Treatment

• Avoid foods that cause allergic reaction
  • Requires careful reading of package labels, especially for those with nut allergies
    • Many products are co-produced in factories where nut residue may be present
    • Warnings on packages do not correlate with actual risks
• Patients with documented severe food allergies or children with allergies and coexistent asthma must have epinephrine kits readily available
• Allergen immunotherapy – associated with significant adverse side effects (desensitization)

Prevention

• Avoid cow milk and dairy products until 6 months old
  • Suggest breast feeding
  • Soy-based formulas have no role in prevention
• Avoid supplemental feeding and solid foods until 6 months old

Tests generally appear in the order most useful for common clinical situations

Guidelines

• Boyce JA, Assa'ad A, Burks AW, Jones SM, Sampson HA, Wood RA, Plaut M, Cooper SF, Fenton MJ, Arshad SH, Bahna SL, Beck LA, Byrd-Bredbenner C, Camargo CA Jr, Eichenfield L, Furuta GT, Hanifin JM, Jones C, Kraft M, Levy BD, Lieberman P, Luccioli S, McCall KM, Schneider LC, Simon RA, Simons FE, Teach SJ, Yawn BP, Schwaninger JM. Guidelines for the diagnosis and management of food allergy in the United States: report of the NIAID-sponsored expert panel. J Allergy Clin Immunol. 2010; 126 (6 Suppl) :S1-58.PubMed
• Boyce JA, Assa'ad A, Burks AW, Jones SM, Sampson HA, Wood RA, Plaut M, Cooper SF, Fenton MJ, Arshad SH, Bahna SL, Beck LA, Byrd-Bredbenner C, Camargo CA Jr, Eichenfield L, Furuta GT, Hanifin JM, Jones C, Kraft M, Levy BD, Lieberman P, Luccioli S, McCall KM, Schneider LC, Simon RA, Simons FE, Teach SJ, Yawn BP, Schwaninger JM. Guidelines for the Diagnosis and Management of Food Allergy in the United States: Summary of the NIAID-Sponsored Expert Panel Report. J Allergy Clin Immunol. 2010; 126 (6) :1105-1118.PubMed
• Boyce JA, Assa'ad A, Burks AW, Jones SM, Sampson HA, Wood RA, Plaut M, Cooper SF, Fenton MJ. Guidelines for the Diagnosis and Management of Food Allergy in the United States: summary of the NIAID-sponsored expert panel report. J Am Diet Assoc. 2011; 111 (1) :17-27.PubMed
• Eigenmann PA, Beyer K, Wesley Burks A, Lack G, Liacouras CA, Hourihane JO, Sampson HA, Sodergren E. New visions for food allergy: an iPAC summary and future trends. Pediatr Allergy Immunol. 2008; 19 Suppl 19 :26-39.PubMed
• Fiocchi A, Assa'ad A, Bahna S. Food allergy and the introduction of solid foods to infants: a consensus document. Adverse Reactions to Foods Committee, American College of Allergy, Asthma and Immunology. Ann Allergy Asthma Immunol. 2006; 97 (1) :10-20.PubMed
• Food allergy: a practice parameter. American Academy of Allergy, Asthma and Immunology - Medical Specialty Society. American College of Allergy, Asthma and Immunology - Medical Specialty Society. Joint Council of Allergy, Asthma and Immunology - Medical Specialty Society. 2006 March. NGC:004958

General

• Berni Canani R, Ruotolo S, Discepolo V, Troncone R. The diagnosis of food allergy in children. Curr Opin Pediatr. 2008; 20 (5) :584-589.PubMed
• Bush RK. Approach to patients with symptoms of food allergy. Am J Med. 2008 May; 121 (5) :376-8.PubMed
• Chafen JJ, Newberry SJ, Riedl MA, Bravata DM, Maglione M, Suttorp MJ, Sundaram V, Paige NM, Towfigh A, Hulley BJ, Shekelle PG. Diagnosing and managing common food allergies: a systematic review. JAMA. 2010; 303 (18) :1848-1856.PubMed
• Eckman J, Saini SS, Hamilton RG. Diagnostic evaluation of food-related allergic diseases. Allergy Asthma Clin Immunol. 2009; 5 (1) :2-.PubMed
• Ito K, Urisu A. Diagnosis of food allergy based on oral food challenge test. Allergol Int. 2009; 58 (4) :467-474.PubMed
• Kim JS. Food allergy: diagnosis, treatment, prognosis, and prevention. Pediatr Ann. 2008; 37 (8) :546-551.PubMed
• Lieberman JA, Sicherer SH. The diagnosis of food allergy. Am J Rhinol Allergy. 2010; 24 (6) :439-443.PubMed
• Sastre J. Molecular diagnosis in allergy. Clin Exp Allergy. 2010; 40 (10) :1442-1460.PubMed
• Shaker M, Woodmansee D. An update on food allergy. Curr Opin Pediatr. 2009; 21 (5) :667-674.PubMed
• Sicherer SH, Sampson HA. Food allergy. J Allergy Clin Immunol. 2010; 125 (2 Suppl 2) :S116-S125.PubMed
• Wang J, Sampson HA. Food allergy. J Clin Invest. 2011; 121 (3) :827-835.PubMed

Allergic Disease
Anaphylaxis
Celiac Disease
Eosinophilic Diseases
Mast Cell Disease