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Types of Food Intolerance

On this page you will find information about food intolerance, including the symptoms of food intolerances and resources to help manage it. We have Factsheets available to help you work out whether you have a food allergy or food intolerance and we can also provide support when it comes to identifying your food intolerance. You can find all of our Factsheets at the bottom of this page.

What is Food Intolerance?

Some people experience adverse reactions caused by food. Finding out which foods are causing your symptoms can be straightforward for some people and incredibly tricky for others - dependent on what their symptoms are, how quickly the symptoms appear after eating the food and which food (or foods) is causing a problem.

Food Intolerances can take some time to diagnose. Although not life threatening, food intolerance can and often does, make the sufferer feel extremely unwell and can have a major impact on working and social life. Ongoing symptoms can also affect the person psychologically as they feel they will never get better. Food intolerance reactions do not involve IgE antibodies or the immune system, like food allergy.

The mechanisms for most types of food intolerance are unclear. Reactions are usually delayed, occurring several hours and sometimes up to several days after eating the offending food. The symptoms caused by these reactions are usually gut symptoms, such as bloating, diarrhoea, constipation and IBS, skin problems such as eczema and joint pain.

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Common Food Intolerances

Histamine Intolerance

Histamine, tyramine and phenyl ethylamine are vasoactive amines (also known as Biogenic Amines), chemicals which occur naturally in certain foods.


Most people tolerate the amounts found in a normal diet. However, some people experience symptoms to even normal levels of vasoactive amines, which may be due to a reduced ability to break them down in their digestive systems. Symptoms of histamine intolerance include:

  • Headaches,
  • Rashes, flushing
  • Runny or blocked nose
  • Diarrhoea, nausea or vomiting
  • Symptoms may occur 30 minutes or longer after eating and the level of intolerance does vary from person to person


Once food allergy or other causes have been ruled out, the best way to establish if vasoactive amines are causing symptoms of histamine intolerance is to try avoiding them for 2-4 weeks. Symptoms need to be monitored by keeping a food and symptoms diary; then by reintroducing foods gradually, you can see how much can be tolerated and how often.

Foods high in histamine, which may cause histamine intolerance, include wine and cheese.


We have further information about histamine intolerance available at the bottom of this page. Our Factsheet talks about topics such as vasoactive amines and foods and drinks that are particularly high in them.

Lactose Intolerance

This is a common disorder arising from an inability to digest lactose (milk sugar) because of low levels of the enzyme lactase. Lactose is the main sugar in milk and milk products from mammals (e.g. humans, cows, goats). Lactose intolerance is often confused with milk allergy, but it is NOT an allergy.


The symptoms of lactose intolerance are: 

  • Diarrhoea
  • Bloating
  • Flatulence (wind)
  • Abdominal pain or discomfort
  • Infantile colic
  • And less commonly, it can cause constipation and nausea.


Lactose intolerance is treated by following a low lactose diet. Most children and adults with lactose intolerance can tolerate small amounts of lactose in foods. Lactose may act as a prebiotic - feeding healthy gut bacteria and improving the absorption of minerals such as calcium, so try to include it if you can.

We have further information about lactose intolerance available at the bottom of this page. Our Factsheet talks about topics such as low lactose diet and milk substitutes for older children and adults. 

Gluten Intolerance / Gluten Sensitivity

Gluten intolerance is a comparatively newly recognised condition, although there is still a lot of controversy as to whether or not it exists and whether it is caused by gluten or another protein found in wheat. It is unclear if it is an intolerance or whether the immune system is involved and it is also unclear if it is lifelong or whether it is a temporary condition.


Patients commonly report a mixture of symptoms in response to eating wheat which include:

  • Abdominal pain
  • Altered bowel habit
  • Bloating
  • Nausea
  • Reflux

However gluten intolerance is also associated with symptoms outside the gut such as:

  • Foggy mind
  • Joint pains
  • Fatigue
  • Depression
  • Headaches
  • Anxiety
  • General lack of well being


Presently there are no tests for gluten intolerance and diagnosis is made by excluding coeliac disease and wheat allergy and using wheat elimination to see if symptoms resolve followed by wheat reintroduction to determine if symptoms reappear. Patients should be referred to a specialist dietitian who can guide them through the appropriate dietary regimen.

We have further information about gluten intolerance in our Reactions to Wheat Factsheet available at the bottom of this page. Our Factsheet talks about topics such as coeliac disease, intolerance due to gut fermentation and foods which are likely to contain wheat.

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