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A food intolerance is when you have difficulty digesting certain foods or ingredients in food. It's not usually serious, but eating the food you're intolerant to can make you feel unwell.

If you have a food intolerance, you usually get symptoms a few hours after eating the food or ingredient you're intolerant to.

Common symptoms include:

• diarrhoea
• bloating
• farting
• tummy pain

But there are lots of other possible symptoms, including headache, feeling tired or exhausted, feeling sick, constipation, joint pain or rashes.

Symptoms can last for a few hours or days.

Food allergy

A food intolerance is different to a food allergy, which causes symptoms such as itchy skin, wheezing or swelling of the lips, face and eyes.

See a GP if:

Call 999 if:

A food intolerance is caused by your body not being able to digest a certain food or an ingredient in food.

The most common food intolerance is lactose intolerance. This is when your body is not able to digest lactose, a type of sugar mainly found in milk and dairy products such as cheese and yoghurts.

But you can be intolerant to any type of food or ingredient in food, such as:

• gluten (wheat, rye and barley) – found in foods like bread and pasta
• histamine – found in foods and drinks like wine and cheese
• caffeine – found in coffee, tea and some fizzy drinks
• alcohol
• sulphites – found in cider, beer and wine
• salicylates – found in some fruits, vegetables, herbs and spices
• monosodium glutamate (MSG) – found in ripened fruits, cured meats and savoury foods

Unlike a food allergy, a food intolerance is not caused by your immune system overreacting to certain types of food, which means you cannot have a serious allergic reaction.

You may be referred to a food and nutrition specialist (dietitian) if a GP thinks you have a food intolerance.

Tests you may have include:

• a special diet where you avoid eating the food you might be intolerant to, to see if your symptoms get better – after a few weeks you start eating the food again to see if your symptoms return
• blood tests
• a breath test if you might be lactose intolerant

You may also be asked to keep a food and symptoms diary to help work out what may be triggering your symptoms.

Home tests

Some tests you can buy that claim to diagnose food intolerances are not recommended.

There's limited evidence that they give accurate results and they may suggest you should avoid multiple foods, which can be harmful.

If you have a food intolerance, try to avoid or reduce eating the food you're intolerant to, including foods where you're intolerant to any of the ingredients.

But it's important to not cut foods out of your or your child's diet without the advice of a GP or food and nutrition specialist (dietitian).

This is because you or your child could miss out on certain vitamins and minerals, which are especially important for a child's growth and development.