Food Allergy

A food allergy is an immune reaction that happens soon after eating a particular food, usually within minutes to two hours. It is different from food intolerance, which involves digestion rather than the immune system and is generally not dangerous. Testing helps tell the two apart so that diets are restricted only where there is a genuine allergy.

Signs of a food-allergic reaction

• Itching or tingling in the mouth
• Hives, flushing or swelling of the lips and face
• Stomach cramps, vomiting or diarrhoea
• Wheeze, cough or a tight throat
• In severe reactions (anaphylaxis): difficulty breathing, a drop in blood pressure, dizziness or collapse

Common trigger foods

Milk, egg, wheat, soya, peanut, tree nuts, fish and shellfish account for most food allergies, though any food can be involved. Many children outgrow milk and egg allergy; peanut, tree nut and shellfish allergy more often persist.

How food allergy is investigated

Detailed history

The single most useful step is a clear account of what was eaten, how soon symptoms started, what they were, and whether the same food has caused problems before.

Testing

Skin-prick testing and specific IgE blood tests measure sensitisation to individual foods. Component-resolved diagnostics can add detail by looking at the particular proteins involved, which helps judge the level of risk. A test result on its own does not confirm allergy — it is interpreted alongside your history.

Supervised food challenge

Where the picture is unclear, a carefully monitored food challenge in the clinic can confirm or rule out allergy and, in some cases, show that a food has been outgrown.

Living with a confirmed food allergy

• Learn to read ingredient labels and recognise the names your allergen can appear under
• Tell restaurants and hosts clearly, and carry safe snacks when travelling
• If prescribed an adrenaline auto-injector, carry two at all times and know how to use them
• Have a written emergency plan and share it with family, school or workplace
• Attend reviews — allergies and advice change over time, especially in children

When to book an appointment

See us after any reaction you think was caused by a food, if you are avoiding foods “just in case” without a diagnosis, or if a child with a known allergy is due for reassessment. Any reaction involving breathing difficulty or collapse is a medical emergency — use an auto-injector if you have one and call for emergency help.

This page is general information and not a substitute for a consultation. Symptoms overlap between conditions, so a clinician's assessment is the reliable way to know what is going on and what will help in your case.