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Identifying your Food Intolerances

Some people experience adverse reactions caused by food. These reactions 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), the airways (such as nasal congestion, shortness of breath or a tight chest), painful joints, headaches or through generally feeling unwell. Some people put up with symptoms for years, which could improve 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 the food and which food (or foods) is causing a problem. This factsheet 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 someone living with an intolerance.

The problem is knowing how and where to get that help, to ensure you don’t fall into the hands of unreliable practices and irrelevant tests. There are many tests available on the high street and on the internet, which appear 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 may not solve the problem, the reason being that allergy tests should be done under the supervision of a conventionally qualified doctor or allergy specialist nurse. Tests are only part of obtaining a diagnosis – a thorough review of the person’s clinical history, symptoms and an informed interpretation of tests in light of this is essential. Many people have positive test results that do not mean that they are allergic to that particular allergen but just sensitised, with a raised level of specific IgE antibodies (this is called atopy).

There are health food shops on the high street offering ‘allergy’ or ‘intolerance’ tests and advertisements in newspapers and magazines for ‘nutritionists’ and ‘allergists’ without any clear indication of training or expertise, making it difficult for someone with a possible condition to find the right help.

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 an accurate and detailed food and symptoms diary alongside a food exclusion diet. The diet needs to be followed strictly for at least a month for purposes of diagnosis. This exclusion is then followed by a period of structured reintroduction of foods one by one, with a gap of three days between each new food introduced. An accurate food and symptom diary must be kept throughout this period. 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 are prepared to keep a food and symptom diary.

By accurately recording the times and duration of all symptoms, illness or stress and exercise, 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 registered dietitian) who is helping you.

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

  • You should not undertake an elimination and reintroduction diet without dietetic help and supervision 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 for 2 weeks 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 need to replace the 'avoided' food with alternatives, shop for these first. Most large supermarkets have a good selection of alternative or ‘free from’ foods and guidance is available from Allergy UK Helpline. Often, you do not need to buy a ‘free from’ food, as there are many natural alternatives, e.g., replace bread / wheat / gluten with rice cakes or oatcakes (check labels for wheat or gluten); replace pasta with rice, millet or quinoa.
  • Do not try to do an elimination and reintroduction diet when you are unlikely to be able 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 other 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 a 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 – 48 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 for Health and Clinical Excellence) Guidelines recommend AGAINST tests such as IgG testing, Vega testing, hair analysis and kinesiology because the results are not relevant or based on sound 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. . If you wish to see a private registered dietitian you can find one by contacting the British Dietetic Association www.bda.uk.com, where you can also check the qualifications of all registered dietitians.

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 Helpline 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. There are also useful recipe books when you know what foods you need to avoid.



Last update: July 2016                    Next review date: July 2019
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