Allergies: Problem foods - is it an allergy or intolerance?

What Is a food allergy?

A food allergy is an immune system response. It occurs when the body mistakes an ingredient in food - usually a protein - as harmful and creates a defence system (antibodies) to fight it. Allergy symptoms develop when the antibodies are battling the 'invading' food. The most common food allergies are peanuts, tree nuts (such as walnuts, pecans and almonds), fish and shellfish, milk, eggs, soya products and wheat.

What is food intolerance?

Food intolerance is a digestive system response rather than an immune system response. It occurs when something in a food irritates a person’s digestive system or when a person is unable to properly digest or breakdown, the food. Intolerance to lactose, which is found in milk and other dairy products, is the most common food intolerance.

What are the symptoms of food allergy?

Symptoms of a food allergy can range from mild to severe, and the amount of food necessary to trigger a reaction varies from person to person. Symptoms of food allergy may include:

• Rash or hives
• Nausea
• Stomach pain
• Diarrhoea
• Itchy skin
• Shortness of breath
• Chest pain
• Swelling of the airways to the lungs
• Anaphylaxis

What are the symptoms of food intolerance?

Symptoms of food intolerance include:

• Nausea
• Stomach pain
• Gas, cramps or bloating
• Vomiting
• Heartburn
• Diarrhoea
• Headaches
• Irritability or nervousness

How common are food allergies and intolerances?

Food allergies affect about 2 to 4% of adults and 6 to 8% of children. Food intolerances are much more common. In fact nearly everyone at one time has had an unpleasant reaction to something they ate. Some people have specific food intolerances. Lactose intolerance is the most common food intolerance.

What causes food allergies and intolerances?

Food allergies arise from sensitivity to chemical compounds (proteins) in food. They develop after you are exposed to a food protein that your body thinks is harmful. The first time you eat the food containing the protein, your immune system responds by creating specific disease-fighting antibodies (called immunoglobulin E, or IgE). When you eat the food again, it triggers the release of IgE antibodies and other chemicals, including histamine, in an effort to expel the protein 'invader' from your body. Histamine is a powerful chemical that can affect the respiratory system, gastrointestinal tract, skin or cardiovascular system.

As a result of this response, allergy symptoms occur. The allergy symptoms you have depend on where in the body the histamine is released. If it is released in the ears, nose and throat you may have an itchy nose and mouth, or trouble breathing or swallowing. If histamine is released in the skin you may develop hives or a rash. If histamine is released in the gastrointestinal tract you will probably develop stomach pains, cramps or diarrhoea. Many people experience a combination of symptoms as the food is eaten and digested.