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Identifying your Food Intolerances

It is known that food can cause many different types of reactions in the body.  These may be evident in the skin (such as hives, rashes, itchiness, or swellings); the gut (such as reflux, vomiting, tummy pains, wind, diarrhoea, and constipation); when breathing (such as shortness of breath or a tight chest) or through generally feeling unwell.  Some people put up with symptoms for years, which could get better if the foods causing these symptoms were cut out of the diet.

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 a food; and which food (or foods) is causing a problem.  This fact sheet can help you explore how you might identify which foods might be causing a problem.

Identifying the food trigger or triggers and a sensible management plan can allow life to be very different for the intolerance sufferer.

The problem is knowing how and where to get that help to ensure you don’t fall into the hands of unreliable practices and tests.  There are many tests available on the high street and on the internet seeming to offer solutions to the problem.  However, scientific and clinical evidence for these tests is usually dubious and even where validated tests such as IgE blood tests are offered for allergy they are unsuitable; the reason being that any allergy tests should be done under the direction of a qualified Doctor.  Tests are only part of obtaining a diagnosis – a thorough review of the person’s clinical history and an informed interpretation of tests in light of this is essential.

These are often health food shops on the high street offering ‘allergy’ tests and advertisements in newspapers and magazines for ‘nutritionists’ and ‘allergists’ without any clear indication of training or expertise.  So, just how does a sufferer find their way through this maze and get on the right path.

Food Intolerance Testing 

The Gold Standard, and only reliable way, to find out which foods are causing adverse reactions in an individual, is by keeping a very clear food and symptoms diary alongside a food exclusion diet.  The diet needs to be followed strictly for purposes of diagnosis.  This exclusion is then followed by a period of structured reintroduction of foods one by one, whilst keeping an accurate food and symptom diary all along.  This is the most reliable way of ‘testing’ for any adverse reaction to a food.  This is best done under the supervision of a registered dietitian.  GPs can refer suitable candidates to a dietitian.  This method of diagnosis is ideally most suitable for people who are prepared to follow the advice strictly and be prepared to keep a food and symptom diary.

By accurately recording the times and duration of all symptoms, illness or stress, as well as everything you eat and drink, you should be able to identify suspect foods.  This includes all prescribed medicines and other supplements, all sweets, nibbles and even licking the mixing bowl when cooking! 

This diary should be continued until the culprit foods causing the symptoms have been identified.

It is helpful to keep food packaging for reference for the health care professional (preferably a dietitian) helping you.

If you do decide to try a simple elimination and reintroduction diet, remember the following basic points:

  • You should never undertake an elimination and reintroduction diet without supervision and dietetic help if you have ever had a severe allergic reaction to anything, in case this happens again when reintroducing a food back into the diet.  Discuss this with your GP if this is the case
  • Keep a food and symptom diary before you commence the exclusion diet as a benchmark of your diet and symptoms.  If you have an appointment with a dietitian take this diary with you.  This should be kept for at least two weeks to identify your most commonly eaten foods and pattern of symptoms
  • Plan in advance.  If you will need to replace the 'avoided' food with alternatives, shop for these first.  Do not try to do an elimination and reintroduction diet when you are unlikely to stick to it rigidly.  If you have an important social occasion looming, are working away from home, or going on holiday, it may be better to start at a later date

  • Try eliminating one food or food group at a time.  Animal milks and dairy products, wheat and gluten, eggs and coffee, are probably the most common foods that cause intolerance problems,  but any food can be a problem so be open-minded.  Foods will need to be avoided strictly for an initial two week period.  If your symptoms improve significantly during this time then this suggests that the food may be responsible for reactions

  • The second part of the test is the reintroduction - eat a normal portion of the food that you have been avoiding, and look for your typical symptoms developing over the next  24 hours.  If nothing happens, have a second portion of the food the following day and assess for symptoms again.  If symptoms are provoked, then continued avoidance of the food is required 
  • In the case of children, medical advice should always be sought, and foods should not be restricted without the guidance of a dietitian as this may result in a nutritionally inadequate diet and poor growth
  • Elimination and challenge diets are not always easy, so it is better to get the support you need rather than just give up.

You should not avoid foods or food groups for an extended period without seeking professional advice, to ensure that your diet remains nutritionally sound.  Because both allergy and intolerance tends to occur with frequently eaten foods, the best plan is always to eat the widest possible variety of foods in your diet, and not to progressively eliminate more and more foods.  The reintroduction stage of the diet is just as important as the exclusion in order to get a clear reliable diagnosis.

Should I still take a test for food intolerance?

No, do not be tempted to do this.  Recent NICE (National Institute of Clinical Excellence) guidelines recommend AGAINST tests such as IgG testing, Vega testing, hair analysis and kinesiology because the results are unreliable and not based on sound thorough scientific evidence.

Dietary advice

Your General Practitioner or practice nurse may have an interest in food intolerance or may be able to refer you to a dietitian specialising in food intolerance.  However, if you decide to opt for a private appointment with a nutritionist it is vital their qualifications are checked out.  If the person holds a degree or equivalent level qualification in nutrition from a recognised university or is a member of the British Association of Nutritional Therapists then generally you will be in safe hands.  To find a registered nutritionist in your area go to www.bant.org.uk   If you wish to see a private dietitian you can find one by contacting the British Dietetic Association www.bda.uk.com or the Health Professions Council.

Allergy UK is able to help people with food intolerance by providing a dedicated telephone helpline on 01322 619898, and factsheets on a wide range of foods and how they can cause reactions. 

The team can provide information about the difference between food allergy and food intolerance, and advise you on keeping a food and symptoms diary, a major tool in helping to identify the food trigger. 


Last updated: October 2012