Food allergy

• Food Hypersensitivity:

  • Reproducible, abnormal, non-psychologically adverse reaction to food
• Food Allergy:

  • Immune-mediated adverse reaction that occurs reproducibly on exposure to a specific food in susceptible individuals
• Food Intolerance:

  • Non-immune mediated reaction to food
  • Could be pharmacological, toxic, metabolic
• IgE-Mediated Food Allergy:

  • Prevalence globally: 3-10% in children
  • SAFFA Study in South Africa: 2.5% in urban areas, 0.5% in rural areas
  • Common allergens: Egg, milk, peanut, wheat, tree nuts, fish, soy, shellfish
  • Chances of outgrowing an allergen is allergen-specific:
  • Egg, cow milk: 50% by 2-3 years
  • Peanut, sesame: 20%
• Food Protein-Induced Proctocolitis:

  • Non-IgE immune-mediated inflammation in the distal colon in response to food proteins
  • Common allergens: Cow’s milk, soy, egg, wheat, corn
• Food Protein-Induced Enterocolitis (FPIES):

  • Non-IgE mediated food allergy that manifests with delayed repetitive vomiting and diarrhea on exposure to an allergen
  • Prevalence: 0.22-0.7%
  • Common food allergens: Cow’s milk, soy
  • Classification: Acute, chronic, atypical
• Mixedeosinophilic Oesophagitis:

  • Chronic immune-mediated or antigen-mediated oesophageal disease characterized by symptoms related to oesophageal dysfunction due to eosinophilic inflammation
  • Prevalence: 0.4% in children and adults
  • Common symptoms: Feeding problems, food dysphagia, impaction
• Diagnosis and Management:

  • History of typical symptoms
  • Reproducibility
  • Gold standard: Admit for food challenge
  • Treatment: Elimination with in-hospital reintroduction or challenge 6 months - 1 year after last reaction
• Skin Prick Test:

  • Advantages: Cheap, results in 15-20 minutes, patient involvement
  • Disadvantages: Off antihistamines for 72 hours, dematographism, small risk of anaphylaxis
• Specific IgE Test:

  • Advantages: Safe, no need to withdraw medication, not influenced by skin disease, larger range of allergens
  • Disadvantages: Expensive, results delayed, possible over-testing
• Oral Food Challenges:

  • Used when diagnosis is unclear or to determine tolerance in another form
  • Types: Open food challenges, double-blinded
• Management:

  • Education
  • Avoidance
  • Action plan and emergency
  • Pharmacotherapy: Adrenaline and antihistamine
  • Immunotherapy: OIT/EPIT/SLIT
  • Regular follow-up for development of tolerance
• Prevention:

  • Maternal factors: Unrestricted diet, natural birth, antibiotics
  • Optimizing eczema control
  • Early oral tolerance: Exclusive breastfeeding for 4-6 months, early introduction of allergenic foods
• Take Home:

  • Food allergy is an immune-mediated adverse reaction to food
  • IgE-mediated reaction is immediate, non-IgE mediated is delayed onset
  • Management of IgE-mediated allergy includes education, avoidance, action plan, adrenaline, and immunotherapy
  • Prevention strategies include optimizing eczema treatment, early introduction of allergenic foods, and enhancing the microbiome