Food Allergy

Overview

A food allergy happens when your body's defence system, the immune system, wrongly treats a food protein as a danger. Even a tiny amount of that food can trigger symptoms. Food allergy is not the same as food intolerance, which does not involve the immune system in the same way.

Food allergy is common, especially in young children. Many children outgrow allergies to milk, egg, wheat, or soy, while allergies to peanut, tree nuts, fish, and shellfish are more often lifelong.

Food allergy can affect anyone at any age. It is often first noticed in babies and young children, but adults can develop new food allergies too.

Symptoms

Common symptoms

• Itchy skin rash, hives, or redness
• Swelling of the lips, face, or around the eyes
• Tingling or itching in the mouth
• Stomach pain, nausea, vomiting, or diarrhoea
• Runny nose, sneezing, or itchy eyes
• Cough or wheeze

Symptoms in children

• Eczema flare-ups or a rash around the mouth
• Vomiting or stomach pain after eating a food
• Refusing food, feeding problems, or poor weight gain if the diet is very limited
• Fussiness or distress after eating a problem food

Symptoms in older adults

• Food allergy can start in later life, even if you have eaten the food before without problems
• Symptoms are usually the same as in other adults
• Reactions may be more serious if you already have heart or lung disease

Causes

Main causes

• The immune system mistakenly treats a harmless food protein as a threat
• Common trigger foods include milk, egg, peanut, tree nuts, soy, wheat, fish, shellfish, and sesame
• Reactions can happen after eating, touching, or sometimes breathing in the food, although breathing in food is rare
• Food intolerance is different and does not involve the immune system in the same way

Risk factors

• Family history of allergy, asthma, eczema, or hay fever
• Having eczema, especially in early childhood
• Being a young child, as some food allergies are more common in children
• Having one allergy can make other allergies more likely, but it does not mean you will get them

When to see a doctor

See a doctor urgently if:

• You have a reaction with swelling, vomiting, or trouble breathing — call emergency services first
• A mild reaction happens for the first time
• A reaction is getting worse or not settling
• A child has repeated feeding problems, vomiting, or poor growth

Book a routine appointment if:

• You think a food is causing symptoms
• You need an allergy action plan or advice about avoiding a food
• You want to discuss testing, school or workplace needs, or travel
• You need help keeping a healthy diet while avoiding foods

Diagnosis

A doctor asks about your symptoms, when they happen, which foods were eaten, and your family history. Tests may be suggested, but they are only useful alongside your story. Do not remove major foods from your diet without medical advice, especially for children.

Tests that may be done

• Food and symptom diary
• Skin prick test, where a small prick is made on the skin with food extract
• Blood test for food-specific antibodies called IgE — antibodies are immune proteins
• Oral food challenge, where tiny amounts of the food are eaten under close medical supervision
• Short elimination diet, only with medical or dietitian advice

What to expect at your appointment

Diagnosis can take time. Some tests can be positive even when you are not truly allergic, so a specialist may need to confirm. Your doctor will help you understand what the results mean for you.

Treatment

The main treatment is avoiding the problem food and being ready for a reaction. There is no cure for food allergy, but most people can manage it well with a clear plan.

Self-care at home

• Avoid the food and read ingredient labels every time
• Ask about ingredients and cross-contact when eating out
• Carry a written allergy action plan and any prescribed emergency medicine
• Teach family, friends, school, and workplace what to do in a reaction
• Wear or carry medical ID if your doctor advises it
• Know that 'may contain' means the food might be present by accident

Medical treatments

Doctors may prescribe emergency medicine for severe reactions, such as an auto-injector, and everyday allergy medicines for mild symptoms. Some specialist centres offer carefully supervised treatments to help the body tolerate a food, but this is not right for everyone. Never use someone else's medicine or change a plan without your doctor.

When is surgery considered?

Surgery is not used to treat food allergy.

Living with this condition

Plan ahead for meals, school, work, and travel. Keep safe foods with you and check labels. Tell people around you about the allergy and your action plan.

Lifestyle tips

• Build meals around safe foods so your diet stays balanced
• Try new foods at home or with medical advice if you are at risk
• Keep emergency contacts and your allergy plan handy
• Review labels because recipes can change
• Plan travel with translated allergy cards and safe snacks

Diet and exercise

A healthy diet is possible with a food allergy. A dietitian can help replace missing nutrients. Exercise is fine for most people; if you have reactions linked to exercise after eating, ask your doctor about timing and precautions.

Mental health and emotional wellbeing

Food allergy can cause worry, stress, and feeling left out. This is common. Talk to your doctor or a counsellor if it affects daily life. If you feel in crisis or unsafe, contact your local emergency number or a local crisis support service.

Prevention

Not all food allergy can be prevented. Current UK and international guidance suggests that introducing common allergy foods to babies around the right age may reduce the risk of some allergies, especially in high-risk infants. Ask your doctor, health visitor, or dietitian before starting, especially if your baby has severe eczema or a known allergy.

Vaccines

There is no vaccine to prevent food allergy.

Screening programmes

There is no routine screening test for food allergy. Testing is used when symptoms suggest an allergy, not to screen everyone.

Complications

If left untreated

• Severe allergic reaction called anaphylaxis, which is a life-threatening emergency
• Accidental exposure because the allergy is not known or planned for
• Poor nutrition or poor growth if foods are removed without dietitian support
• Anxiety, avoidance, and social isolation
• Repeated mild reactions that could have been prevented

Long-term outlook

Most people with food allergy can live full lives with a clear plan. Some children outgrow milk, egg, wheat, or soy allergy; peanut, tree nut, fish, and shellfish allergies are more often lifelong. Regular review helps keep your plan up to date.

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