Food allergy
An immune reaction to a specific food, typically fast and IgE-driven, causing hives, swelling, vomiting or, at its most serious, anaphylaxis. It is distinct from food intolerance, and its diagnosis rests on the story plus specific allergy testing.
What it is
A food allergy is an immune-system reaction to a particular food protein. The classic and most important type is IgE-mediated: within minutes to a couple of hours of eating the food, the body releases histamine and other chemicals, causing hives, itching, swelling of the lips or face, vomiting, tummy pain, and — in the most severe form, anaphylaxis — throat tightening, wheeze, a drop in blood pressure and collapse. Common triggers include peanuts, tree nuts, milk, egg, wheat, soy, fish and shellfish. It is crucial to distinguish true allergy from food intolerance (such as lactose intolerance), which is uncomfortable but not an allergic, life-threatening reaction and does not involve IgE. Diagnosis rests mainly on a clear history of reactions, supported by allergen-specific IgE blood tests or skin-prick testing to confirm the trigger — general blood panels are not the answer. Anyone at risk of anaphylaxis needs an emergency plan and adrenaline auto-injector.
Key lab markers
- Allergen-specific IgE (or skin-prick testing) — the key tests; they confirm sensitisation to a specific food, interpreted with the history.
- Total IgE — often raised in atopic people but non-specific; does not identify the food.
- Eosinophils — may be mildly raised, reflecting allergic tendency.
- Oral food challenge — the definitive test in specialist settings when the diagnosis is unclear.
- Tryptase — can be measured after a severe reaction to confirm anaphylaxis. Unproven 'IgG food intolerance' tests are not recommended and can mislead.
Symptoms
- Hives (raised, itchy welts), flushing, itching
- Swelling of the lips, face, tongue or throat
- Tingling or itching in the mouth
- Vomiting, tummy pain, diarrhoea
- A runny or blocked nose, sneezing, watery eyes
- Anaphylaxis (severe): throat tightness, difficulty breathing, wheeze, dizziness or collapse — a medical emergency
- Symptoms usually start within minutes to two hours of eating
Related symptoms
When to discuss with a doctor
A reaction with any sign of anaphylaxis — throat tightness, difficulty breathing, wheeze, swelling of the tongue or throat, faintness or collapse — is a medical emergency: use an adrenaline auto-injector if prescribed and call for emergency help immediately. For suspected food allergy without a severe reaction, see a doctor to take a careful history and arrange the right tests (allergen-specific IgE or skin-prick), rather than relying on general or unproven tests. A confirmed allergy at risk of anaphylaxis needs an emergency action plan, an adrenaline auto-injector, and specialist allergy input. Mediora.AI can note a raised total IgE or eosinophil count consistent with an allergic tendency, but confirming a specific food allergy and its management belong with your doctor or allergist.