Synopsis
Diagnose immediate food allergy from a reproducible clinical history, use targeted sensitisation testing correctly, distinguish allergy from tolerance and build safe avoidance, nutrition, emergency and school plans.
- IgE-mediated reactions usually begin within minutes and generally within two hours of eating, with urticaria, angioedema, vomiting, wheeze or cardiovascular symptoms.
- Diagnosis starts with the exact food, form, dose, timing, reproducibility, cofactors and treatment response, alongside tolerance of related or previously eaten foods.
- Perform skin-prick testing or serum specific IgE only to foods suggested by the history and interpret results by age, test size or concentration and pretest probability.
- A positive sensitisation test does not prove clinical allergy and a broad panel often creates false labels and unnecessary exclusions.
- A medically supervised oral food challenge is the reference clinical test when history and sensitisation leave meaningful uncertainty; it must occur where anaphylaxis can be treated.
- Do not use serum food-specific IgG, hair analysis, kinesiology, Vega testing or unvalidated home tests to diagnose food allergy.
- Avoid only the confirmed allergen, involve a paediatric dietitian for staple or multiple foods and preserve nutritionally useful tolerated forms unless the specialist plan says otherwise.
- Risk assessment determines whether to prescribe adrenaline auto-injectors; train the child, family and school with the exact device and provide a written emergency plan.
- Asthma control matters because poorly controlled asthma increases the danger of respiratory food reactions and complicates recognition.
- Review allergy over time because milk and egg tolerance can develop; home reintroduction or baked-food ladders are used only for selected children under a documented specialist plan.
Key red flags
Airway, breathing or circulation compromise after food exposure requires adrenaline immediately; antihistamine must not delay first-line treatment.
A previous severe reaction, poorly controlled asthma, trace-trigger reaction or difficulty avoiding the allergen increases future risk and urgency of specialist review.
Infants with faltering growth, multiple exclusions, feeding aversion or restricted diet need early paediatric dietetic assessment to prevent nutritional harm.
A reaction to a tiny amount, a reaction during exercise or cofactor exposure, or an apparently inconsistent trigger requires specialist challenge and cofactor assessment.
Isolated positive IgE or skin testing without a compatible reaction history demonstrates sensitisation, not necessarily clinical allergy.
Persistent dysphagia, food impaction or feeding difficulty raises eosinophilic oesophagitis rather than ordinary immediate food allergy and needs gastroenterology assessment.
Investigation priorities
Estimate clinical probability and select the exact food, form and mechanism for testing.
Management branches
Food exposure causes airway, breathing or circulation compromise.
- Give intramuscular adrenaline immediately and call emergency services under the anaphylaxis algorithm.
- Position safely, support airway, oxygenation and circulation and repeat adrenaline at five minutes if needed.
- Document food, dose, timing, cofactors and treatment for specialist follow-up.