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HealthInfo Waitaha Canterbury

Food intolerance

Many people think they're allergic to a food when in fact they have an intolerance to the food. A food intolerance is an unpleasant reaction to a food, but the reaction doesn't involve your immune system.

This is different from a food allergy, which involves an overreaction by your immune system. If you have a food allergy, a very small amount of food can trigger an allergic reaction within minutes.

In food intolerance, the symptoms usually begin within a few hours of eating the food but can be delayed for up to 48 hours and can last for hours or even days.

Also with a food intolerance, the amount of the food you eat will affect how severe your reaction is.

Causes of food intolerance

Common food intolerances are lactose intolerance, which means you can’t digest lactose – the natural sugar found in milk and some dairy products, and FODMAP intolerance, which is common in people with irritable bowel syndrome.

Other causes of food intolerances include:

Symptoms of food intolerance

Symptoms of food intolerance can vary from mild to severe but aren't life-threatening. They usually include:

For some people, symptoms may include skin rashes, headaches and eczema or asthma getting worse.

Food intolerances can sometimes have the same symptoms as other health conditions, so if you have these symptoms talk to your general practice team.

Diagnosing food intolerance

Food intolerance can often be difficult to diagnose. Tests used to diagnose food allergies such as skin prick tests or blood tests aren't useful for diagnosing food intolerance.

Several tests including cytotoxic food testing, Vega testing, kinesiology, iridology, pulse testing, Alcat testing, reflexology, hair analysis and IgG food antibody blood testing have been promoted for diagnosing food intolerance and food allergy. These tests do not have any scientific basis and haven’t been shown to be accurate or reliable.

You’ll need to be checked for other conditions that could be causing your symptoms.

It may help to keep a diary to record if certain food or drinks make your symptoms worse.

The only reliable way to determine if a food or drink is causing your symptoms is to stop eating it for a least two weeks and keep a diary of your symptoms.

If your symptoms do not improve, it’s unlikely that you’re intolerant to that food. If your symptoms get much better, it’s likely the food is a problem.

Treating food intolerance

You can either avoid the food or reintroduce the food gradually to work out how much you can tolerate. It’s best to do this under the guidance of a dietitian, especially if you suspect you or your tamariki (child) are intolerant to several foods. This is important, as prolonged restrictive diets can lead to problems getting the nutrition you need, particularly for tamariki.

Written by HealthInfo clinical advisers. Page created July 2022.


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Review key: HIALL-38559