Do you have a food intolerance?

Information regarding food allergy and intolerance is plentiful, but so are the myths. Self-diagnosed, food sensitivities have become more common place, but how can you really tell if you suffer from a food intolerance?

Stomach pain

Food allergy and food intolerance

Food intolerances are different to food allergies. An allergy elicits an acute, almost immediate reaction; the worst of which is anaphylaxis. Food intolerance is less severe and notoriously difficult to test. Intolerance is usually because the body is lacking an enzyme that is needed to properly digest and eliminate a food or substance. Symptoms may be delayed and might include bloating, headaches or skin rashes. Skin prick testing and laboratory blood tests are available but the most effective, accepted and accurate way of identifying problem foods is via an elimination diet.

Elimination diet

Vegetables in box
An elimination diet is a free, non-invasive way of working out if you have a food sensitivity. You don’t need any pills or potions, just a fair amount of will power. Compliance and commitment are key to getting results. However, an elimination diet should be followed for the shortest time possible to bring about symptom improvements.

Before you embark on an elimination diet, arm yourself with all the information you might need. Consult a qualified health professional to ensure your nutritional requirements are met and to address any other considerations. For example, where testing for coeliac disease is recommended, do not eliminate any foods from your diet until the tests have been completed.

Start by removing suspected foods and food groups – dairy, eggs, caffeine and alcohol (to name a few) for 6-8 weeks. A useful practical tool is to create a comprehensive list of ‘foods to exclude’ and ‘foods to include’ and to keep a food diary of how you feel, your symptoms and their severity etc.

After the period of elimination, reintroduce one food at a time from the exclusion list in normal amounts. Test the food on its own on an empty stomach. If symptoms return within 48 hours, then you probably have your answer. Leave at least two days between testing different foods.  If there is no reaction after four days, bring the food carefully back into your diet. If you do experience a reaction, wait until you feel well again before continuing the reintroduction and avoid the culprit food for three months before re testing.

If you suspect you have an allergy or intolerance or if you are breastfeeding, pregnant or taking any medication, you should consult with your doctor before making any dietary adjustments.  

Common intolerances


Fructose is a natural sugar found in fruits, honey and some syrups. If you suspect you have a sensitivity to fructose, you should also try to avoid sucrose (table sugar), high fructose corn syrup, fruit and fruit juices, sorbitol and sweetened juices. Common signs of fructose intolerance include abdominal pain, gas and bloating and diarrhoea. The FODMAP diet is a new approach to managing IBS which may be effective in this circumstance.


is one of the most commonly cited foods for causing digestive upsets including abdominal bloating. When trying to decipher wheat intolerance, it is important to eliminate flour and flour based products entirely as well as other foods which may contain wheat or wheat-derived ingredients. Wheat intolerance varies between individuals with some people able to tolerate alternative grains. If you suspect you have wheat intolerance, try eliminating wheat entirely. You may find that you can tolerate small amounts of older varieties of grains such as spelt or kamut which are higher in fibre, lower in gluten and more nutritious.


Gluten is the glue-like protein found in many grains but especially in wheat, rye and barley. Its elasticity makes it a key part of many bakes. Some people are intolerant to the gluten in all of these grains, others just find wheat the trigger. A diet high in refined carbohydrates can contain significant quantities of gluten, which can effectively ‘glue up’ the digestive system. If you have discovered you cannot tolerate any gluten containing grains, try rice, corn and potato flours. However, before you embark on any elimination diet, be sure to consult your GP. It is essential that if you suspect gluten to be a problem that you make no changes to your diet until you have completed all of the appropriate medical tests to determine what the problem may be. This is because if you eliminate gluten before tests are completed for coeliac disease then you risk a false negative result. 


Sugar in hands
Glucose intolerance is the umbrella term given to metabolic conditions which cause elevated blood glucose levels. If you have impaired glucose tolerance (IGT) or impaired fasting glucose (IFG), your body is not using glucose (sugar) properly. This may result in higher than normal blood sugar levels – a condition known as hyperglycemia. Diagnosis of either IGT or IFG requires medical guidance and is through blood test. Symptoms include excessive thirst, dry mouth, fatigue, blurred vision and frequent urination. It is important to seek medical advice if you suspect you have an intolerance to glucose.  


Pouring milk into glass
All animal milks contain a sugar called lactose. We make an enzyme in our gut called lactase to digest the lactose in milk. Without lactase, the sugar is left to ferment in the gut and causes symptoms such as bloating, wind and diarrhoea. Many adults do not produce enough lactase, so suffer from what is known as lactose intolerance (essentially a lactase deficiency). Those who are intolerant to lactose you may be able to tolerate a little butter, cheese or yogurt before symptoms arise. Others choose to avoid dairy products completely.


Glass of wine
Alcohol intolerance may be caused by alcohol or the food the alcohol is made from (e.g. grapes from wine, grains from whisky). Alcohol can affect the integrity of the gut which may explain why some people experience digestive discomfort to food when it is coupled with drinking alcohol. Red wine is a common trigger, followed by whisky and beer. Alcohol intolerance can cause unpleasant symptoms such as nasal congestion and skin flushing. Once again, intolerance is linked to an enzyme deficiency making it hard for the body to break down alcohol. Intolerance may also be due to other ingredients commonly found in alcoholic beverages (especially beer and wine) including sulphites, preservatives or chemicals.


Glass of beer
Histamine occurs naturally in certain foods. We produce an enzyme called diamine oxidase to help break down the histamine in certain foods. Like with many intolerances, some people do not produce enough of this enzyme and consequently when they eat histamine containing foods they suffer symptoms such as headaches, skin rashes, itching, diarrhoea and abdominal pain. Foods that are particularly high in histamine include: wine, beer, cider, pickled foods, cheese, tofu, soya sauce, processed meats, smoked fish and chocolate.  More information on histamine intolerance can be found at


Loaf of bread
Yeast is present in a variety of foods, commonly bread, baked products and alcoholic beverages. Yeast intolerance has a wide range of symptoms including flatulence, bad breath, fatigue, irritability, cravings for sugary foods, stomach cramps, bad skin and indigestion. If you suspect you are intolerant to yeast try following a yeast free diet (through elimination) for a few weeks. If there is a significant improvement then you have found your culprit!

For more information on food intolerances visit

This article was last reviewed on 24 January 2019.

Kerry Torrens is a qualified Nutritionist (MBANT) with a post graduate diploma in Personalised Nutrition & Nutritional Therapy. She is a member of the British Association for Nutrition and Lifestyle Medicine (BANT) and a member of the Guild of Food Writers. Over the last 15 years she has been a contributing author to a number of nutritional and cookery publications including BBC Good Food.

Jo Lewin is a registered nutritionist (RNutr) with the Association for Nutrition with a specialism in public health. Follow her on Twitter @nutri_jo.

All health content on is provided for general information only, and should not be treated as a substitute for the medical advice of your own doctor or any other health care professional. If you have any concerns about your general health, you should contact  your local health care provider. See our website terms and conditions for more information.

Comments, questions and tips

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ThePhilosophy's picture
8th Jun, 2018
Hello all, I would imagine you are on this page because you either have an intolerance to certain foods, or you know someone who has. Unfortunately, this condition is a growing one. I have tolerated it for 37 years. Starting off with eggs, chicken and pork, I only linked the symptoms, to the offending food-stuffs, in my mid-20's. Living without chicken and pork isn't so bothersome, but living a life free of eggs is annoying, to say the least. Going out for dinner tends to be an initial interrogation of ignorant and bewildered staff, who scurry from table-side to kitchen, asking 'Chef' if there really are eggs in mayonnaise? '...because the bearded guy is telling me there is'. Does the chips have their own fryer? Is the batter egg-less? Do you deep-fry chicken in the same oil as...? Cross-contamination happened quite recently in a supermarket cafe. I decided on the safe-bet of toast. It was after consuming the second piece, that I noticed a yellow edge to the cut line. A horrific picture jumped into my mind, of a bacon and egg sandwich being cut, just before the same knife was used on my toast. Needless to say, I had a miserable afternoon, mainly looking for public conveniences. In the last 10 years matters have got worse and my intolerance has grown to all farmed meats, including farmed salmon, trout, halibut etc. I can still enjoy wild fish, which begs the question, have I become more sensitive, or has farming practice changed? There has always been antibiotics used in the poultry and pig industry. In practice, intensive fish, poultry and animal rearing has a major risk, which could see the entire stock lost in a very short time. An outbreak of disease could spread rapidly in a salmon cage, with 300,000 salmon, so preventative measures are needed to sustain the health of the overcrowded cage. I imagine insurance companies would not even consider insuring the livestock, unless it could be proven that every effort was being made to keep the stock alive. There is ultimately a cost for chicken going cheap and salmon for all. I guarantee the cost will be picked up by the consumers and the environment. I also guarantee the growing trend of intolerance within the population. Year 1 biology informed us of food-chains, so it is not like new news. Charlie
15th Apr, 2016
Of course you are lactose intolerant. You are not a calf !!!!!!! What people don't realize is that if they cut out all animal products (meat, eggs and dairy) most people don't have problems with bread, yeast, fructose, gluten, wheat and so on. (unless you have an actual disease) Eat a plant based whole food diet and your problems will go away before you even get them!
Life Of Diva
1st Dec, 2014
The food we eat plays an important role in keeping our skin healthy. Fresh fruits and vegetables are always good for our health and give us a glowing skin too. Studies conducted on people shows that those people who consumed proper amount of vitamins and minerals in their diet have healthier skin and hair than those who did not. Protein rich foods, vitamins and carbohydrates help to nourish the cells in our body and promote growth and development. When our body lacks proper nourishment, it reflects on our skin as it gets dry and dehydrated. Here are some fabulous foods for dry skin you need to check out below:
16th Jun, 2014
All i can suggest on this is that everyone should eat food regularly they should skip to eat like eat crashing so that they would have a sexy body. Food is very important to our body so we should take it in right time. For more information kamagra jelly
2nd May, 2014
Why wasn't salicylate sensitivity mentioned? It is very difficult to eliminate this from the diet as it means few fruits, vegetables, no preservatives or artificial additives. No organic produce, no herbs, no spices, no tea or coffee, or flavored drinks and only a couple of alcoholic drinks and milk and water. Labels must be read carefully when you have this intolerance. Also food intolerances can lead to anaphylaxis as I well know. It does not develop suddenly instead builds up over several hours or days, but is very serious when the throat is swelling.
13th Nov, 2013
Hi although you make the disclaimer about consulting GP before making any dietary changes I think it is important that you highlight the need to have conditions such as Coeliac Disease excluded BEFORE anything is taken out of the diet. So often people remove gluten, feel better, then they are denied a proper diagnosis and thus treatment package. Gluten needs to be in the diet so that serology testing and biopsy doesn't give a false negative result. People will follow your advice without seeking medical help.
23rd Jan, 2014
Absolutely right! I've made a similar comment elsewhere on this site - it is really important to exclude coeliac disease before starting an elimination diet.
Kaz Knuckles's picture
Kaz Knuckles
24th Dec, 2017
what causes chronic heartburn when i eat sausage rolls or pies fried chips too ?
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