Food Allergies and Intolerances

Food Allergies and Intolerances

Food Allergies and Intolerances

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Food Allergies and Intolerances - Friend or Foe?

⭐ Type I hypersensitivity (IgE-mediated) is the most common mechanism in true food allergies, characterized by rapid onset of symptoms.

  • Food Allergy: Immune reaction (IgE/non-IgE mediated) to food components.
  • Food Intolerance: Non-immune adverse reaction (e.g., enzyme deficiency, pharmacologic).
FeatureFood AllergyFood Intolerance
MechanismImmune (IgE/non-IgE)Non-immune (enzyme defect)
OnsetRapid (mins-hrs) / DelayedGradual (hrs-days)
SymptomsMulti-system (skin, GIT, resp.)GIT (bloating, pain, diarrhea)
SeverityLife-threatening possibleNot life-threatening
  • Common Allergens:
    • Cow's milk
    • Egg
    • Peanut
    • Wheat
    • Soy
    • Fish
    • Shellfish
    • Tree nuts

Common Food Allergens and Reactions

  • Clinical Manifestations by System:

    SystemManifestations
    CutaneousUrticaria, angioedema, atopic dermatitis exacerbation
    GIVomiting, diarrhea, abdominal pain, FPIES
    RespiratoryAllergic rhinitis, asthma, laryngeal edema
    SystemicAnaphylaxis (hypotension, bronchospasm)

⭐ Cow's milk protein allergy is the most common food allergy in infancy and early childhood, often outgrown by age 5.

  • Food Protein-Induced Enterocolitis Syndrome (FPIES): Profuse, repetitive vomiting 1-4 hours post-ingestion; lethargy, pallor, diarrhea. Can lead to dehydration, shock. Common triggers: cow's milk, soy, rice, oats. No IgE involvement typically.

Food Allergies and Intolerances - Unmasking Allergies

  • Initial Steps: Detailed history (symptoms, timing, suspected foods), physical exam.
  • IgE-Mediated Tests:
    • Skin Prick Test (SPT): Wheal ≥3mm > negative control. Positive predictive value varies. Skin Prick Test Interpretation and Example
    • Specific IgE (sIgE) blood test: Quantitative; higher levels suggest ↑ likelihood of clinical allergy.
  • Elimination Diet: Remove suspected food(s) for 2-4 weeks; monitor symptoms.
  • Oral Food Challenge (OFC):
    • Confirms diagnosis after positive tests or supervised reintroduction.

⭐ Double-Blind Placebo-Controlled Food Challenge (DBPCFC) is the gold standard for diagnosing food allergy, though an open Oral Food Challenge (OFC) is often used in clinical practice.

Food Allergies and Intolerances - Dodging & Defusing

  • Allergy: IgE-mediated (e.g., nuts, milk). Intolerance: Non-IgE (e.g., lactose).
  • Diagnosis: History, SPT, sIgE. OFC (gold standard).
  • Anaphylaxis Management:
    • 📌 Epinephrine dose: $0.01 \text{ mg/kg}$ IM (max 0.3mg pre-pubertal, 0.5mg pubertal/adult) anterolateral thigh.
    • Auvi-Q Epinephrine Auto-Injectors for Pediatric Patients

⭐ Prompt administration of intramuscular epinephrine is the cornerstone of anaphylaxis management and can be life-saving.

  • Prevention: Strict dietary avoidance. Written emergency action plan. Educate on EAI use.

Food Allergies and Intolerances - Gut Grumbles

  • Food Allergy: IgE-mediated (e.g., urticaria, anaphylaxis) or non-IgE-mediated (e.g., FPIES).
  • Food Intolerance: Non-immunologic (e.g., lactose intolerance).
Lactose Intolerance TypeCauseOnset
Primary↓ Lactase persistence (genetic)Late childhood/Adult
SecondaryGut mucosal injury (e.g., infection)Any age
CongenitalAutosomal recessive, rare $LCT$ mutationBirth
DevelopmentalPrematurity (< 34 wks)Neonatal

📌 BLAB for lactose intolerance symptoms: Bloating, Loose stools, Abdominal pain, Borborigmi (rumbling).

High‑Yield Points - ⚡ Biggest Takeaways

  • Cow's Milk Protein Allergy (CMPA) is the most frequent food allergy in early infancy.
  • Distinguish IgE-mediated (rapid onset) from non-IgE-mediated (delayed) reactions.
  • Oral Food Challenge (OFC) remains the gold standard for definitive diagnosis.
  • Intramuscular epinephrine is the first-line treatment for anaphylaxis.
  • Key allergens: milk, egg, soy, wheat, peanuts, tree nuts, fish, shellfish.
  • Lactose intolerance (enzyme deficiency) is distinct from CMPA (immune response).
  • FPIES causes severe, delayed gastrointestinal symptoms like profuse vomiting_

Practice Questions: Food Allergies and Intolerances

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Flashcards: Food Allergies and Intolerances

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The dose of vitamin A prophylaxis for a 1-yr-old child would be _____ IU orally.

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