Food Allergy And Intolerance

Overview

A food allergy happens when your immune system - your body's defence system - mistakes a harmless food for a threat and attacks it. This can cause symptoms within minutes, and in some people it can be serious. A food intolerance is different. It does not involve the immune system and it is not life-threatening, but it can make you feel very uncomfortable, often a few hours after eating. Because the two can feel similar, it is easy to confuse them - but they need different care, so it helps to know which one you may have.

Yes. Food allergy is one of the most common long-term conditions in childhood. In the UK and many other countries, roughly 1 in 12 children and 1 in 50 adults have a food allergy. Food intolerance is even more common - lactose intolerance alone affects a large share of adults worldwide. If you think food is affecting you, you are certainly not alone.

Anyone can develop a food allergy or intolerance at any age. Food allergy most often starts in the first two years of life, especially in babies with eczema or with a family history of allergy, asthma or hay fever. Some allergies, such as shellfish and fruit allergies, are more likely to appear in adult life. Food intolerance is more common in adults than children, and some types are more common in people from particular ethnic backgrounds because of genetic differences in how the body digests certain sugars.

Symptoms

Common symptoms

• Tingling or itching in the mouth, or an itchy throat
• Raised, itchy red bumps on the skin (hives), or a red, itchy rash
• Swelling of the lips, face, tongue, or puffiness around the eyes
• Stomach pain, feeling sick, vomiting, or diarrhoea
• A blocked or runny nose, sneezing, or itchy, watery eyes
• Wheezing, cough, or shortness of breath
• For intolerance: bloating, wind, stomach cramps, loose stools, headache, or feeling hot and flushed - usually several hours after eating

Symptoms in children

• Eczema that keeps flaring, or skin that reacts after certain foods
• Being very unsettled or colicky after feeds, or reflux that keeps coming back
• Blood or mucus in the stool
• Poor weight gain or slower growth
• Vomiting or diarrhoea soon after a particular food
• Refusing food, or a baby becoming clingy, pale and floppy during a reaction

Symptoms in older adults

• A food allergy can start in later life, though this is less common than in childhood
• Digestive symptoms that get blamed on ageing or on a medicine may actually be food intolerance
• New skin rashes, itching, or swelling after eating
• Low appetite or weight loss, especially if foods have been cut out without advice
• Some long-term conditions and some medicines can make a reaction more serious - check with your doctor

Causes

Main causes

• Immediate food allergy: the immune system makes allergy antibodies (called IgE) to a food protein. These trigger cells to release chemicals such as histamine, causing symptoms within minutes.
• Delayed food allergy: the immune system reacts in a slower way, with symptoms starting hours later. This pattern is more common in babies and young children, for example with cow's milk.
• Food intolerance: the body cannot properly break down or absorb part of a food. Lactose intolerance, for example, happens when the gut does not make enough of the enzyme that digests milk sugar.
• Other conditions that look like allergy: coeliac disease is an immune reaction to gluten, but it works differently from a food allergy and needs its own tests.
• Additives and natural chemicals: rarely, substances such as sulphites or natural histamine in some foods can cause reactions that look like allergy.

Risk factors

• A close family member with allergy, asthma, eczema, or hay fever
• Eczema in early childhood
• Already having one allergic condition, such as hay fever or asthma
• Being male in early childhood (food allergy is slightly more common in boys)
• Some ethnic backgrounds have higher rates of food allergy and lactose intolerance
• Low vitamin D levels and changes in the gut bacteria in early life have been studied as possible factors
• Delaying the introduction of foods like peanut and egg past around 6 months may raise the risk; early introduction appears to help for many babies

When to see a doctor

See a doctor urgently if:

• Any reaction with breathing difficulty, throat swelling, or fainting - call your local emergency number straight away
• A reaction that needed an emergency auto-injector device - always get medical help afterwards, even if you feel better
• Sudden swelling of the face, lips, or tongue
• A child with blood in the stool, repeated vomiting, or poor growth
• Symptoms that keep getting worse over hours, or signs of dehydration

Book a routine appointment if:

• You think a food is making you unwell and want to find out for certain
• You or your child have had a mild reaction such as hives or stomach upset after eating
• You are already avoiding foods and want help doing it safely
• Your child has eczema, colic, or slow growth that might be linked to food
• You want to know whether you have an allergy or an intolerance before making big diet changes

Diagnosis

Your doctor will start by listening to your story: which foods, how soon after eating, what symptoms, and how often. That history is the most important part of the diagnosis, because tests alone can be misleading. They may ask you to keep a food and symptom diary, or to try a short, supervised period without the suspected food and then bring it back. If an allergy is likely, you may be referred to an allergy clinic for skin or blood tests, and sometimes a supervised food challenge, where you eat the food in a safe setting so staff can watch for a reaction.

Tests that may be done

• Food and symptom diary kept over a few weeks
• A trial of removing the food, then reintroducing it - the most reliable way to confirm an intolerance
• Skin prick test: a tiny drop of food extract is placed on the skin and the skin is gently pricked
• Blood test for allergy antibodies (specific IgE) to a particular food
• Supervised food challenge in a clinic - the most accurate test for food allergy
• Breath test for lactose intolerance, or a blood test for coeliac disease, if those are suspected
• Note: alternative tests such as kinesiology, hair analysis, or IgG food 'intolerance' tests are not reliable and are not recommended

What to expect at your appointment

Working out a food problem can take several weeks rather than one appointment. You may be asked to keep a diary, note exactly when symptoms start, and bring a list of everything you eat. Removing a food takes at least a few weeks before you can judge whether it helps - and the food should always be reintroduced to confirm the answer, ideally with medical or dietitian support. Be patient with the process; a careful answer is worth more than a quick guess, and no single test gets it right every time.

Treatment

There is no cure for food allergy, but it can be managed very well. The main approach is to avoid the food you react to, know exactly what to do if a reaction happens, and have any emergency treatment your doctor has recommended with you at all times. For intolerance, the answer is usually adjusting how much of the food you eat rather than cutting it out completely. A dietitian is often the best person to help you keep your diet safe, varied, and balanced.

Self-care at home

• Keep a written record of what you eat and how you feel, so patterns become clear
• Read food labels every time - recipes and ingredients can change without warning
• Ask about ingredients and cross-contamination when eating out, and check before ordering
• Carry a written allergy action plan and any emergency device your doctor has prescribed, and check its expiry date
• Make sure family, friends, school, and workplace know what to do in a reaction
• Consider a medical alert bracelet or card so others know about your allergy in an emergency
• Do not cut out many foods or major food groups without advice - a dietitian can help you avoid gaps in nutrition
• For suspected lactose intolerance, try smaller portions of dairy, or have milk with meals, and see how you feel

Medical treatments

Your doctor's plan will depend on whether you have an allergy or an intolerance. For allergy, the plan is built around avoiding the food, having a written emergency plan, and - if your reactions have been severe or you have asthma as well - carrying an emergency auto-injector device that you have been trained to use. Doctors may recommend anti-allergy medicines for mild symptoms such as hives or itching, and a reliever inhaler if wheezing is part of your reaction. In specialist centres, some people are offered carefully supervised treatments that gradually build tolerance to a food, or treatments for related allergic conditions such as asthma or eczema. For intolerance, medicines do not fix the problem; adjusting how much and how often you eat the food is usually enough, and a dietitian can help you plan this. Always follow the plan your own doctor gives you, and never borrow someone else's prescription medicine.

When is surgery considered?

Surgery is not used to treat food allergy or food intolerance.

Living with this condition

Life with a food allergy or intolerance becomes easier with routines. Plan meals and snacks ahead, keep safe foods with you, and get into the habit of reading labels and asking questions when eating out. Many people find it helpful to contact restaurants in advance and to carry a card listing their foods. For a child, agree a clear plan with the school or nursery and make sure staff know what to do. For intolerance, you will learn by experience how much of a food your body can handle - that flexibility usually makes daily life much easier than strict avoidance.

Lifestyle tips

• Build a short list of trusted meals and snacks you can rely on
• Shop with a plan, and check labels each time you buy something, even if you have bought it before
• Speak to restaurants or caterers ahead of time, and be clear about cross-contamination
• Keep your emergency plan and device with you, and check expiry dates regularly
• Teach friends, family, and colleagues what a reaction looks like and how to help
• Wash hands and surfaces when preparing food for someone with an allergy, and avoid sharing utensils
• Travel prepared: pack safe snacks, carry your plan, and know how to explain your needs in the local language
• Have a dietitian review if you avoid several foods, to keep vitamins, minerals, and protein topped up

Diet and exercise

A balanced diet is still possible with almost any food allergy, but it may take some planning. If you avoid milk, make sure you get calcium and vitamin D from other sources; if you avoid wheat, look at fibre and B vitamins; if you avoid nuts or fish, look at protein and healthy fats. Your doctor or dietitian can suggest suitable alternatives and, if needed, supplements. Exercise is good for your general health and mood, but if you have a food allergy and asthma, make sure your asthma is well controlled and follow your action plan - exercise can sometimes make a reaction worse, so never exercise alone straight after a reaction.

Mental health and emotional wellbeing

Living with a food allergy can be genuinely stressful. Eating out, parties, school trips, and holidays can all bring worry, and some people feel anxious or left out. This is very common and it is not a sign of weakness. Talking to your doctor, a dietitian, or a counsellor can help, and support groups let you share tips with people who understand. If low mood or anxiety is affecting your sleep, work, or relationships, please reach out for help. If you ever have thoughts of harming yourself, contact your local emergency number or a crisis support line in your country straight away - you deserve immediate support.

Prevention

Food allergy cannot always be prevented, and it is not anyone's fault. Current evidence suggests some things may lower the risk: breastfeeding where possible, not delaying the introduction of common allergens such as well-prepared peanut and cooked egg from around 6 months (for most babies), and offering these foods regularly once introduced. If your baby has severe eczema or an existing allergy, talk to your doctor or health visitor before introducing peanut or egg - they may suggest a check first. Only avoid a food if a health professional has advised it, because unnecessary avoidance can do more harm than good. Food intolerance is not preventable in most cases, but symptoms can usually be managed well.

Vaccines

There is no vaccine for food allergy or food intolerance. Keeping other vaccinations up to date is still important, because infections can make any long-term condition harder to manage.

Screening programmes

There is no routine screening test for food allergy or intolerance. Testing is only useful when there are symptoms to explain, because tests on their own can give false alarms and lead to foods being avoided needlessly. If you have a strong family history of allergy, or your baby has severe eczema, mention it to your health visitor or doctor so you can plan the introduction of new foods together.

Complications

If left untreated

• A serious allergic reaction (anaphylaxis), which can be life-threatening if not treated quickly
• Repeated accidental reactions because the trigger has not been identified
• Poor growth, low iron, or low vitamin levels - especially in children on restricted diets
• Unnecessary food avoidance, which can narrow the diet and affect nutrition and quality of life
• Anxiety around eating, eating out, and social events, and sometimes feeling isolated
• Ongoing discomfort from intolerance affecting sleep, work, and school

Long-term outlook

The outlook is generally good. Many children grow out of milk, egg, and wheat allergy by school age, and peanut allergy is now treatable in specialist centres for some people. Food intolerance can usually be managed well simply by adjusting portions. The key is getting a clear answer, having a plan you understand, and regular reviews with your healthcare team. Most people with a food allergy or intolerance live full, active, and enjoyable lives - with a bit of planning and the right support around them.

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