Food allergies & intolerances


People often confuse food allergies and food intolerances, but the two are actually completely different.

What is a food allergy?

This happens when the body's immune system, which protects the body from infection, sees a specific food as a threat. This leads to an immune response in which chemicals such as histamine are released into the body, triggering a range of different allergy symptoms. Some can be mild, whilst others can be life-threatening. With a food allergy, you won't be able to tolerate the particular food at all. Even the smallest amount can cause very severe symptoms.

What are the most common causes of food allergies?

Although allergic reactions can occur with any foods, common causes include:

• Peanuts

• Tree nuts (almonds, walnuts, Brazil nuts, pine nuts, pecans and cashews)

• Milk

• Eggs

• Fish

• Shellfish

• Wheat

• Soy

• Fruit (apples, peaches, strawberries and kiwi fruits)

What sort of symptoms can you expect?

A food allergy can cause different symptoms in different parts of the body at the same time. These include:

• An itchy, burning sensation inside the mouth, throat or ears

• A raised itchy red rash (called urticaria or hives) anywhere on the body

• Swelling of the face, around the eyes, lips, tongue and roof of the mouth (known as angioedema)

• Nausea and vomiting

• Hayfever-like symptoms such as sneezing and itchy eyes

• Diarrhoea

• Shortness of breath or wheezing (anaphylaxis). This is a life-threatening response that can cause sudden difficulty in breathing, a rapid heartbeat and collapse

What should you do in the event of an anaphylactic reaction?

Symptoms of anaphylaxis include breathing difficulties, light-headedness and feeling faint or close to losing consciousness. Emergency treatment for anaphylaxis is an immediate injection of adrenaline. People at risk of experiencing severe allergic reactions are usually prescribed an adrenaline auto-injector pen, which can be used in emergencies. If either you or anyone you're with develops the symptoms of anaphylaxis, the adrenaline auto-injector should be used first, before calling for an ambulance immediately after. Ask for an ambulance and tell the operator that the person has anaphylaxis or is in anaphylactic shock.

Can you be tested for a food allergy?

If you suspect you or your child has a food allergy, make sure you make an appointment with your GP. They will ask you a set of questions to help determine if it is a food allergy. If they suspect it is, your doctor may refer you for a skin prick test at an allergy clinic.

This can help to identify the substances you're allergic to. The test involves putting a drop of liquid onto your forearm, containing a substance you may be allergic to. The skin under the drop is then gently pricked. If you're allergic to the substance, an itchy, red bump will appear within 15 minutes.

This should be done by professionals. Food allergies can also be diagnosed by taking a blood test. You may also be put on a food elimination diet, which, if you have a food allergy, should never be tried without discussing with a qualified healthcare professional.

In a food elimination diet, the food suspected of causing the allergic reaction is removed from the diet for two to six weeks. The food is then slowly reintroduced and any symptoms monitored.

What’s the treatment for food allergies?

Antihistamines can be used to treat the symptoms of a mild to moderate allergic reaction to food. A number of antihistamines are available over-the-counter without a prescription. Make sure you always have these at hand, in case you eat the food by mistake.

Some over the counter antihistamines are not suitable for children under two. Speak to you Doctor  if you have a young child with a food allergy for advice on what antihistamine might be suitable. If the reaction is potentially life-threatening (a risk of severe angioedema or anaphylaxis), your Doctor will prescribe an auto-injector adrenaline pen and teach you how to self-inject.

You should carry the auto-injector with you at all times and also keep one at home and at work or school. In the event of an anaphylactic episode, the adrenaline should be injected immediately and an ambulance called.

What is food intolerance?

Food intolerance results in a negative reaction to a particular food or ingredient. It often happens when the body doesn't produce enough of the specific enzyme needed to digest that food. Symptoms come on slowly, often many hours after eating the problem food. It can leave you feeling uncomfortable, but it doesn't cause a serious illness and is not life threatening.

What are the most common causes of food intolerance?

• Dairy products such as milk, yogurts and soft cheeses. These all contain lactose, a type of sugar, which many people, especially children, find difficult to digest

• Wheat, found in foods such as bread, pasta, cereals and couscous

Food intolerances can also be caused by food additives and chemicals such as:

• Caffeine

• Alcohol

• Artificial sweeteners

• Monosodium glutamate (MSG)

• Artificial colours, preservatives or flavour enhancers

What sort of symptoms can you expect?

• Stomach pain

• Bloating

• Wind

• Diarrhoea

• Skin rashes and itching

Can you be tested for food intolerance?

There are no specific tests for food intolerances. To find out if you have one, you'll need to keep an eye on your symptoms and the food you eat. The best way to do this is to keep a food diary. Make a note of everything you eat during the day and what, if any, symptoms you experience.

Also note when these symptoms occur. Once you have a good idea of which foods might be giving you a problem, you may want to consider trying an elimination diet. This involves cutting out the suspected problem foods one by one from your diet, for a period of two to six weeks and observe if your symptoms improve. The targeted foods can then be gradually reintroduced to see if the symptoms return.

You may find you can tolerate a certain amount and only have symptoms if you go over this amount. Consider speaking to a dietitian before starting an elimination diet to make sure your diet is still balanced whilst doing this trial. You should never restrict a child's diet unless under the supervision of a dietician or a doctor.

Could my symptoms be caused by something else?

If you are persistently getting diarrhoea, bloating, stomach pain or skin rashes, you should see your GP. They can help to rule out other health problems that have similar symptoms and may take blood tests.

Other conditions with similar symptoms include:

• Irritable bowel syndrome (IBS) – a condition that affects the digestive system

• Coeliac disease – an autoimmune response to gluten in which the small intestine becomes inflamed

• Inflammatory bowel disease – inflammation of the gut

Living with a food allergy or intolerance

Once you've identified your food allergy or intolerance, awareness is key. This means always reading food labels and asking about ingredients when eating out. 

Wherever possible, cook food from scratch so you know exactly what you are eating. If you think your child may have an allergy or intolerance, talk to your Doctor about the best way to manage it. They may refer you to a specialist for further tests.