Food allergy vs food intolerance: what is the difference?

Written by: Professor James Lindsay
Edited by: Conor Dunworth

In his latest online article, leading London-based gastroenterologist Professor James Lindsay explains the difference between a food allergy and a food intolerances.


When might someone worry that they have a food allergy?

Many people come to the clinic and ask whether they may have a food allergy. You may worry that you have a food allergy if you experience any of the following symptoms after you eat:

  • if your gut hurts
  • loose stool
  • vomiting
  • tingling/itching in the mouth or throat


What is the difference between a food allergy and food intolerance?

It’s really important to differentiate between a food allergy and a food intolerance.

In medical terms, an allergy is very specific. It's an immune reaction against certain aspects of the food, usually proteins within the food. Two common allergies that beget significant reactions are shellfish and peanuts. Exposure to these foods can cause anaphylactic shock in people who are allergic to them. This is an immune reaction to those foodstuffs.


Coeliac disease is also an immune reaction of the immune cells that line the gut. They react with one of the proteins that is contained in gluten. People with celiac disease go on a gluten-free diet.

But that doesn't mean that every time someone gets symptoms from what they eat, it's actually an allergic reaction. And of course, the food that we eat can very much give us symptoms in the bowel. If we eat too many fermentable carbohydrates, we may get bloating, we may suffer from loose stool, and we may get wind.

For example, eating foods such as baked beans can cause you to pass a lot of wind. Now, if you're particularly sensitive to the development of that gas, you may feel that when you eat certain foods, you always get symptoms. However, this is not an allergy, it’s an intolerance.

If you are having symptoms when you eat, it's important to get some advice to try and differentiate between the two. Your doctor can help you if you need treatment for an allergy. They can also give you dietary advice, and let you know the foods to avoid that you may be intolerant to.


Professor James Lindsay is a renowned consultant gastroenterologist based in London. If you would like to book a consultation with Professor Lindsay you can do so today via his Top Doctors profile. 

By Professor James Lindsay

Professor James Lindsay is a renowned consultant gastroenterologist based in London, who specialises in the treatment of digestive issues such as inflammatory bowel disease (IBD), irritable bowel syndrome (IBS) and acid reflux. In his twenty-five years of experience, he has also gained bowel cancer colonoscopy accreditation from the National Screening Centre.

After graduating with a degree in medical sciences from the University of Cambridge, Professor Lindsay went on to qualify from the University of Oxford as a bachelor of medicine as well as surgery. He achieved his PhD in mucosal immunology from Imperial College London in 2002, before completing his fellowship with the Royal College of Physicians in 2008.

In addition to his professional experience, he is also passionate about learning and governance in his field. He has been both education officer and governing board member of the European Crohn’s and Colitis Organisation (ECCO). He is currently a member of the International Organisation of IBD (IOIBD) and a national representative for the British Society of Gastroenterology.

He regularly leads pioneering clinical trials and has both written and contributed to numerous medical publications.

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