Food Allergies and the Upper Aerodigestive Tract

Introduction & Epidemiology - Food Facts Fast

• Food Allergy: Immune-mediated (IgE, non-IgE, mixed). Food Intolerance: Non-immune (e.g., lactose intolerance).
• Prevalence: ↑ worldwide; India: estimates vary, ~1-2% in adults, higher in children.
• Common Allergens: Milk, egg, peanut, tree nuts, soy, wheat, fish, shellfish. (📌 MEP TSW FS - My Excellent Professor Teaches So Well, For Sure!)

⭐ Cow's milk protein allergy is the most common food allergy in early childhood.

Pathophysiology - Immune Mayhem

• Immune Responses:
  • IgE-mediated (Type I hypersensitivity): Rapid. Allergen binds IgE on mast cells → degranulation.
  • Non-IgE-mediated: Delayed. T-cell involvement; GI symptoms common.
  • Mixed: Both IgE and cell-mediated pathways active.
• Mediator Release (IgE): Mast cells release histamine, leukotrienes, prostaglandins, cytokines.

• Cross-reactivity: IgE antibodies recognize similar epitopes on different allergens (e.g., pollen-food).

⭐ Oral Allergy Syndrome (OAS) is a Type I IgE-mediated reaction from cross-reactivity between aeroallergens (e.g., birch pollen) and raw fruit/vegetable proteins.

Clinical Manifestations (UADT) - Throat & Nose Alerts

• Oral Allergy Syndrome (OAS)/Pollen-Food Allergy Syndrome (PFAS):
  • Rapid oral itching, mild angioedema (lips, tongue, palate) from raw plant foods.
  • Due to pollen-food cross-reactivity (e.g., Birch pollen ↔ apples, carrots).
• Nasal:
  • Allergic rhinitis: Sneezing, rhinorrhea, nasal congestion, pruritus.
• Throat/Larynx:
  • Pharyngitis: Soreness, irritation.
  • Laryngitis: Hoarseness.
  • ⚠️ Angioedema (laryngeal): Stridor, airway compromise (emergency!).
  • Dysphagia: Difficulty swallowing; consider Eosinophilic Esophagitis (EoE).
• Eosinophilic Esophagitis (EoE):
  • Food-triggered esophageal inflammation; causes dysphagia, food impaction.

⭐ Birch pollen sensitization is commonly linked to OAS with apples, hazelnuts, and carrots.

Diagnosis - Allergy Detectives

• Foundation: Detailed clinical history, meticulous food diary.
• Initial Investigations:
  • Skin Prick Test (SPT): Wheal ≥3mm than negative control.
  • Serum specific IgE (sIgE) levels.
• Further Assessment:
  • Component Resolved Diagnosis (CRD): Clarifies sensitization patterns if results are ambiguous.
  • Oral Food Challenge (OFC): Confirmatory gold standard; guides elimination diets.
• Suspected EoE: Endoscopy with biopsy for Eosinophilic Esophagitis.

⭐ The Double-Blind, Placebo-Controlled Food Challenge (DBPCFC) is the gold standard for diagnosing food allergy, especially in research settings or complex cases.

Management & Prevention - Relief Roadmap

• Foundation: Strict allergen avoidance; comprehensive patient education.
• Emergency Action Plan (EAP):
  • Essential: Epinephrine Auto-Injector (EAI).
    • Dosage: $0.01 \text{ mg/kg}$ (Max: Child 0.3mg, Adult 0.5mg).
    • 📌 EPI for Anaphylaxis: Epinephrine Prevents Incidents.
• Pharmacotherapy:
  • Antihistamines for mild symptoms.
  • Corticosteroids for severe reactions/EoE.
• Emerging Options: Oral (OIT), sublingual (SLIT), epicutaneous (EPIT) immunotherapy.
• Prevention Strategy: Early introduction of allergenic foods.

⭐ Intramuscular epinephrine is the first-line treatment for anaphylaxis and should be administered promptly.

High‑Yield Points - ⚡ Biggest Takeaways

• Oral Allergy Syndrome (OAS) is common, linked to pollen-food associations (e.g., birch-apple).
• Eosinophilic Esophagitis (EoE) involves chronic inflammation, esophageal dysfunction, and eosinophilic infiltration.
• FPIES typically presents with profuse, delayed vomiting and lethargy in infants.
• Anaphylaxis is a severe systemic reaction; epinephrine is the crucial first-line treatment.
• Key diagnostics include skin prick tests and serum specific IgE; oral food challenge is gold standard.
• Laryngeal edema can be a life-threatening manifestation of food-induced anaphylaxis.