II. Epidemiology

  1. Incidence of Food Allergy
    1. Adults: 2-3%
    2. Children: 4-5%
      1. Up to 15% of parents believe their children have Food Allergy, but most cases are unproven
  2. Prevalence of most common specific food allergens
    1. Milk Allergy: 0.9% (up to 6% in studies based on parent or self-report)
    2. Egg Allergy: 0.3% (up to 1% in studies based on parent or self-report)
    3. Seafood allergy: Up to 2.8% of adults (based on parent or self-report)
    4. Peanut allergy: 0.6% (based on parent or self-report)
    5. Tree nut allergy: 0.4% (based on parent or self-report)

III. Risk Factors

  1. Family History of atopic disease (Atopic Dermatitis, Asthma, Allergic Rhinitis)
  2. Tick Bite (lone star tick) predisposes to Alpha-Gal Reaction
    1. Sensitization to galactose-alpha-1,3-galactose (alpha-gal), found in both ticks and red meat
    2. Results in severe, sudden, Allergic Reaction (Urticaria, Anaphylaxis) to beef, lamb, pork

IV. Causes: Common Food Allergies

  1. Children
    1. Cow's Milk Allergy
    2. Egg Whites
    3. Wheat
    4. Soy
    5. Peanuts
  2. Adults
    1. Crustaceans (e.g. shrimp, lobster)
    2. Tree nuts
    3. Peanuts
    4. Fish

V. Causes: Food Allergies associated with Anaphylaxis

  1. Nuts (allergy often seen in Atopic Patients)
    1. Peanuts (legume)
    2. Tree nuts
      1. Pistachios
      2. Walnuts
      3. Cashews
      4. Almonds (and marzipan)
      5. Hazelnuts or filberts
      6. Macadamian Nuts
      7. Pecans
      8. Brazil nuts
      9. Pine nuts
  2. Fish
  3. Shellfish
    1. Crab
    2. Crayfish
    3. Prawns or shrimp
    4. Lobster
  4. Seeds
    1. Sesame seeds
    2. Sunflower seeds
    3. Caraway seeds

VI. Causes: Cross-reactivity with contact or air-borne allergens

  1. See Oral Allergy Syndrome
  2. Latex Allergy
    1. Banana
    2. Kiwi
    3. Avocado
  3. Birch pollen allergy
    1. Carrot
    2. Celery
    3. Hazelnuts
    4. Parsnips
    5. Potatoes
    6. Fresh fruit (apples, cherries, nectarines, peaches, pears)
  4. Grass pollen
    1. Kiwi
    2. Tomato
  5. Ragweed pollen
    1. Bananas
    2. Melons (canteloupe, honeydew, watermelon)

VII. Pathophysiology

  1. Initial reaction (Sensitization)
    1. IgE antibodies produced to food
  2. Subsequent Reaction
    1. IgE fixed to Mast Cells in Skin, GI, Respiratory
    2. Reacts to allergen
    3. Releases
      1. Histamine
      2. Chemotactics attract Eosinophils
      3. Prostaglandins and Leukotrienes are released

VIII. Types: Clinical Presentations of Food Allergies

  1. Emergent presentations
    1. Food-induced Anaphylaxis
    2. Laryngeal Angioedema
  2. Skin reactions
    1. Acute Urticaria (IgE mediated)
    2. Allergic Contact Dermatitis (cell-mediated)
    3. Angioedema (IgE mediated)
    4. Contact Urticaria (IgE and non-Ige mediated)
  3. Gastrointestinal food allergies
    1. Dietary Protein-induced Proctocolitis (non-IgE mediated to milk in infants)
    2. Eosinophilic Esophagitis (IgE and non-IgE mediated)
    3. Food Protein-induced enterocolitis (non-IgE mediated)
    4. Immediate GI Hypersensitivity (IgE mediated)
    5. Oral Allergy Syndrome (cross-reactivity among foods; prevented by cooking offending food)

IX. Symptoms

X. Differential Diagnosis: Postprandial collapse

  1. Airway Foreign Body
  2. Non-allergic food reaction
    1. Monosodium Glutamate
    2. Sulfite reaction
    3. Scombroid Fish Poisoning (vasoactive amines)

XI. Differential Diagnosis: Non-allergic gastrointestinal food reactions

XII. Diagnosis

  1. Immediate Reacting IgE skin Test
    1. Epicutaneous stick with Fresh Food Extract
    2. Sensitive and Specific
    3. Do NOT perform for food suspected of Anaphylaxis
  2. In-Vitro test for allergen-specific IgE Antibodies (RAST)
    1. Less sensitive than skin test
    2. Safe alternative to skin test (Anaphylaxis suspected)
  3. Open Food Challenge
    1. Use for reintroduction of foods after 2-3 years
      1. For foods with less serious reactions
        1. Example: Hives to milk or eggs
    2. Diet diaries
    3. Short-term Elimination Diets

XIII. Management: Milk Allergy or intolerance with GI Symptoms

  1. Differentiate from Infantile Colic
    1. Colic will resolve spontaneously after 3-4 months
    2. Milk substitution is unnecessary
  2. Substitute Casein Hydrolysate (Cow's Milk) Formula
    1. Nutramigen, Pregestimil, Alimentum
    2. Soy-based formula is not appropriate substitution

XIV. Management: Anaphylaxis reaction history

  1. Indefinitely avoid causative food
  2. Epinephrine Self-Injectors for home/school (Should have 2 pens available)
    1. Child over age 6
      1. Epinephrine (1:1000) 0.3 mg SQ (EpiPen)
    2. Child under age 6
      1. Epinephrine (1:2000) 0.15 mg SQ (Epi-Pen Jr)

XV. Management: Reintroduction of prior food allergies

  1. Mix with other foods
    1. Eggs in baked products (instead of scrambled eggs)
    2. Milk in Cheese or yogurt (instead of glass of milk)
  2. Do not reintroduce foods with previous Anaphylaxis
    1. Do not re-introduce nuts, seeds or seafood if prior Allergic Reaction (especially if history of Anaphylaxis)

XVI. Management: Specific food Issues

  1. Egg Allergy and Vaccinations
    1. Indicated Vaccines regardless of egg allergy severity (these Vaccines contain only minute egg amounts)
      1. Measles Mumps Rubella Vaccine (MMR Vaccine)
      2. Varicella Vaccine
    2. Possibly indicated Vaccines
      1. Influenza Vaccine
      2. May be given if egg Allergic Reaction was limited to Urticaria (especially if tolerates egg containing foods)
        1. Consider monitoring for 2 hours after Vaccination
        2. Skin Testing for Influenza Vaccine reaction is not recommended due to high False Positive Rate
    3. Contraindicated Vaccines (if hives, Angioedema, Anaphylaxis to egg)
      1. Rabies Vaccine
      2. Yellow Fever Vaccine
  2. Fish Allergy
    1. Avoid fresh and saltwater fish
    2. Most fish-allergic patients can tolerate canned tuna
  3. Nut allergy (often associated with Anaphylaxis)
    1. See Palforzia (Peanut Allergen Powder)
    2. Do not eat at buffets
    3. Avoid unlabeled candies and desserts
    4. Avoid ice cream parlors
  4. Milk allergy
    1. Avoid not only cow's milk, but also sheep and goat's milk
    2. Avoid butter or margarine containing milk
  5. Crustacean allergy
    1. Avoid all crustaceans (shrimp, lobster, crab...)

XVII. Associated Conditions

  1. Oral Allergy Syndrome
  2. Food dependent Exercise induced Anaphylaxis (rare)
    1. Wheat is most common associated food trigger
    2. Anaphylaxis occurs only if specific food trigger ingested before Exercise
    3. Space Exercise at least 6 hours after trigger food is ingested
  3. Food-induced Urticaria
    1. Food allergies account for 30% of acute cases but rarely cause Chronic Urticaria
  4. Atopic Dermatitis
    1. Improves when eggs, milk and peanuts are removed from diet

XVIII. Associated Conditions: Conditions NOT associated with Food Allergy

  1. Abnormal Child Behavior
    1. Myths:
      1. Hyperactivity, Insomnia, Anxiety (Shannon,1922)
      2. "Allergic Attention Fatigue Syndrome" (Rowe, 1950)
    2. Reality
      1. No proven relationships
  2. Attention-Deficit Disorder (ADD)
    1. Myth: Attention Deficit Disorder related to dietary additives
      1. Dietary Salicylates
      2. Artificial food colors and flavors
        1. Feingold, 1975
    2. Reality
      1. Only 2% ADD Children would benefit from diet change
    3. Reference
      1. Lipton (1983) J Am Diet Assoc 83:132-4 [PubMed]
  3. Sugar "Allergy"
    1. Myth: Refined sugars aggravate behavioral problems
      1. Suggested to provoke hyperactivity, aggressive, inappropriate behavior
    2. Reality
      1. Sugar does not increase activity
        1. Milich (1986) Clin Psychol Rev 6:493-513 [PubMed]
        2. Mahan (1988) Ann Allergy 61:453-8 [PubMed]
      2. Sucrose has "calming effect" when c/w Aspartame
        1. Kruesi (1986) Annu Rev Nutr 6:113-30 [PubMed]
        2. Bachorowski (1990) Pediatrics 86:244-53 [PubMed]

XIX. Prognosis

  1. Transient Food Allergies
    1. Most food allergies last only a few years
    2. Milk, eggs, wheat or soy allergies usually resolve
      1. Egg allergy: 70% resolve by age 5 years
      2. Milk allergy: 85% resolve by age 5 years
  2. Lifelong Food allergies
    1. Foods associated with systemic Anaphylaxis
    2. Nuts, fish, seed allergies persist

XX. Prevention

  1. Recommended strategies to prevent Food Allergy
    1. Exclusive Breast Feeding until 4-6 months of age
    2. Solid food introduction by 6 months of age
      1. Potentially allergenic foods may be introduced at this time
  2. Strategies to avoid (not effective or unsupported)
    1. Maternal dietary restrictions during pregnancy and Lactation are not recommended
    2. Soy infant formula substitution for cow's milk infant formula is not recommended

XXI. Resources

  1. Food Allergy and Anaphylaxis Network
    1. http://www.foodallergy.org

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