The difference between food allergy and food intolerance

While food allergies and intolerances can cause some of the same symptoms, there are some key differences between the two. These should help you differentiate between whether your child is suffering from a food allergy or an intolerance, but it’s always best to seek proper testing from a specialist for food allergies from if you suspect that might be the cause.

Digestive system vs. immune system response
A food allergy is a negative immune system response to a food protein that triggers an allergic reaction. When an allergy occurs, your immune system overreacts, producing Immunoglobulin E (IgE) antibodies which travel to cells and release chemicals that cause an allergic reaction. 90% of all food allergies are caused by the top-eight food allergens, which includes wheat, soy, shellfish, fish, milk, eggs, soy, peanuts and tree nuts. The other 10% of food allergies can come from any food, with some children allergic to products such as red meat, citrus and celery (for example).

Food intolerance, on the other hand, is a negative reaction to a food that doesn’t involve the immune system and instead takes place in the digestive system. Food intolerances are not normally life-threatening. Intolerance reactions normally take much longer to develop (up to 20 hours after consuming food) and occur when your body is unable to digest a certain food properly.

Food allergy symptoms vs. food intolerance symptoms
A food allergy can cause a potentially life-threatening reaction when the food is touched, eaten or even inhaled. This is referred to as anaphylaxis which normally occurs within seconds or minutes of eating food and symptoms include difficulty breathing, dizziness or losing consciousness. Anaphylaxis requires immediate treatment with an adrenaline shot to prevent fatal consequences, and the symptoms include suddenly feeling weak due to a drop in blood pressure and breathing problems as the throat begins to swell up.

Other, nonlife-threatening symptoms of food allergy are either shown on the skin, respiratory or gastrointestinal. The most common symptoms of food allergy include itching, developing a rash or hives. Gastrointestinal symptoms are identified by vomiting or diarrhoea and respiratory symptoms can include shallow breathing, wheezing, chest congestion, coughing, a runny or blocked nose and itchy/watery eyes.
In contrast to food allergies, food intolerance symptoms are focused on the digestive system and common symptoms include diarrhoea, bloating and an upset stomach. Less common food intolerance symptoms include weight loss, lack of energy, headaches and anaemia. These symptoms are often linked to other digestive disorders such as Irritable Bowel Syndrome (IBS and Chron’s Disease).

Food allergy testing vs. food intolerance testing
Food allergy testing can be carried out by an allergy specialist and there are two different ways to test for an allergy. For symptoms that develop quickly (an IgE-mediated food allergy) – a skin prick test or a blood test is the recommended tool for diagnosis. For symptoms that are slowed to develop (a none IgE-mediated food allergy) – a food elimination diet is the best way to diagnose.

There are no food intolerance tests that are currently recommended by the British Dietetic Association, so the best way to identify an intolerance is to keep a food diary and monitor your symptoms. If you suspect a certain food is a cause, cut this out of your diet and see whether your symptoms disappear. You can then slowly reintroduce it to see if this causes your symptoms to flare up again.
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For advice relating to food allergies or intolerances, email me at [email protected] with any questions and I’ll be happy to help.