Frequently Asked Questions About Food Intolerances



Should I take a food intolerance test?
If you are experiencing any of the symptoms that are listed in the following question, and you have checked with your GP to ensure that you have no underlying causes for your symptoms, then a food intolerance test would be a good next step.


What are the symptoms of food intolerances?
Food intolerances can produce a wide range of symptoms and can affect almost any organ. Patients often report multiple symptoms such as digestive pain with headaches and a skin rash, but some of the more common symptoms include:- Anxiety, attention deficit disorder, depression, constipation, diarrhoea, abdominal bloating, inflammatory bowel disease, irritable bowel syndrome, gastritis, insomnia, headaches, migraines, fluid retention, arthritis, fibromyalgia, asthma, chronic fatigue syndrome, itchy skin, weight control problems, and hyperactivity disorder.


Are the tests covered by health insurance companies?
You will need to check with your insurance provider, polices vary from company to company.


What is the difference between food allergy and an intolerance?
A classical food allergy such as peanut or shellfish allergy is typically characterised by an immediate and often severe reaction when exposed to the offending food. Symptoms can include sneezing, skin irritation, rashes, swelling, runny nose, fatigue, and while allergic reactions to foods can vary considerably in their severity, some could be fatal. In these allergic reactions IgE antibodies are usually involved. A food intolerance is often to be characterised by a delayed onset and maybe due to a pharmacological effect such as that caused by the tyramine in red wine, an insufficiency of an enzyme such as in lactose intolerance, or to the production of IgG antibodies to the offending foods. The symptoms of IgG induced food intolerance are often delayed and can occur up to 3 days after eating the food concerned, making it very difficult to determine which foods are causing the problem.


Which test should I take: the test from your clinic or one of the tests you send by post?
This is entirely up to you. If you live close to our clinic in Bristol and want to get your results quickly, you can send us an email, or call us on 0117973 2966 and we can arrange a test for you, usually within a few days. Alternatively, if cannot get to us, or you prefer the test to be carried out in our laboratory, we will provide you with an easy-to-use collection kit and the results will typically be available within less than two weeks.


Why should I use your service rather than another?
We use testing kits in our clinic supplied by Cambridge Nutritional Sciences and YorkTest Laboritories, and use their labs for our postal tests. Both Cambridge Nutritional Sciences and YorkTest Laboritories have been performing ELISA testing for over 25 years.


Will the results differ throughout the day?
No, it does not matter when the sample is taken.


How long will the samples remain stable in the post?
The IgG molecules in the sample are very stable and can easily tolerate up to three weeks in the post, but samples normally take only 1 – 2 days to reach the lab.


What do the borderline foods mean?
The borderline foods are slightly above the normal values and ideally should be reduced to a minimum in your diet. Therefore, we recommend that you rotate those foods showing a borderline result, once every 4 days if possible.


Is it possible to be affected by foods that are not detected by the IgG food test?
Some foods may cause a classical allergic reaction involving the production IgE antibodies. These will not be detected by any IgG food test. There are also many foods that can cause a reaction in the body without involving the immune system but produce symptoms similar to IgG reactions. For example, some food additives such as tartrazine can cause hives, rashes and asthma; monosodium glutamate in Chinese dishes produces sweating and dizziness; amines in chocolate, cheese and red wine may cause migraines; and ‘Nightshade’ alkaloids in potatoes, tomatoes and peppers can affect the joints. These are very difficult to test, but you should avoid them if you suspect they are affecting you.






Are there any drugs that will affect the results?
Immunosuppressants which are generally given following an organ transplant will reduce the immune system’s ability to generate antibodies. High doses of steroids will also affect antibody production. If you are in any doubt, please consult your GP.


How much blood do I need to put in the collection tube?
You need to at least half fill the collection tube with blood. If you do not get this much blood into the tube, then it is possible that any positive results will be weaker than they should be because of a greater dilution of the blood sample.


I don’t seem to be able to collect enough blood, what should I do?
In the unusual circumstances when you have been unable to collect enough blood, and both of the lancets provided have been used, then it may be necessary to telephone CNS for a replacement tube and lancets. It is important to make sure that your hands are warm and that you have massaged your sample finger thoroughly before using the lancet.


Do I have to collect the blood sample at any particular time of day?
No, samples can be collected at any time of the day.


How can so many tests be done on such a small sample of blood?
The methods used by our testing kits at the clinic and by the lab are very sensitive indeed, so concentration of antibodies in serum is very high, and we only need a very small sample of blood for the test. Even a very small sample needs to be diluted before testing. When the collection tube is half full with blood it provides the correct amount of blood required for the test.


What should I do if I am unable to provide a finger prick blood specimen?
Some people find that they cannot easily collect a blood sample. In this case a friend may be able to help with the procedure. Alternatively you could talk with the nurse at your local clinic about obtaining a venous sample. In this case ask the clinic to collect a 3ml plain sample (no anti-coagulant).


I have been avoiding a food for more than 3 months; will this food show up in the test?
It is possible that the antibody levels will have reduced significantly if you have been completely avoiding that food, and therefore highly likely that the food test will be unable to detect any antibodies. If you wish to test whether you can now tolerate the food concerned and feel that you can cope with the symptoms that may occur, include a portion of that food every day for 5-7 days before taking the blood sample. However, if you know that the food concerned causes you extreme symptoms do not to re-introduce that food at all.


Are there any research papers to support these tests?
Yes, a number of studies have implicated food IgG antibodies in the development of food intolerances and chronic illnesses such as eczema, arthritis, irritable bowel syndrome.


Have there been any trials to support these tests?
An independent audit, conducted in 1998, studied symptom reduction in over 2000 individuals following an elimination diet based on the food intolerance IgG test. The audit demonstrated that more than 70% of patients reported a significant reduction in symptoms after eliminating the foods giving high IgG levels in the test.


What is an IgG?
IgG stands for Immunoglobulin G. Immunoglobulins are antibodies which are produced by the immune system in response to foreign bodies entering the body. There are several different types of immunoglobulins with IgA, IgE, IgG, IgM being the most well known.


What is an antibody, and what is the difference between IgG and IgE antibodies?
An antibody is a specialised protein produced by the body’s immune system when foreign bodies (such as viruses, bacteria and toxins) enter the body. They are produced by special white blood cells called B-Lymphocytes as a defence against these foreign substances. IgE antibodies are a type of antibody mostly found in the skin, nose, lining of airways and lungs, and are usually produced in classical allergies. IgG antibodies are the type of antibodies that CNS test for food intolerances. It has been shown by various studies, that if foods that producing high IgG levels are eliminated from the diet, the symptoms of food intolerance can be reduced.


Why do foods cause an IgG response?
Generally, foods are broken down during digestion into their component parts e.g. amino acids, glycerides etc. These pass harmlessly through the gut into the bloodstream. However, occasionally small fragments of partially digested or undigested foods are able to pass through the gut wall into the bloodstream where they are recognized by the immune system as being ‘foreign’. The immune system responds by making antibodies (IgGs). In some patients, inflammation or irritation of the intestinal lining allows partially digested foods to leak into the bloodstream. This condition is called ‘leaky gut syndrome’ and patients with this condition typically have high levels of antibodies to multiple foods.


Why would some members of a food family come up positive (e.g. soya, haricot, kidney) even though not eaten for years, and yet have no reaction to other members (i.e. lentils, carob, peanuts, peas) that have been eaten?
While members of the same food family may be antigenically similar such that antibodies to one member will cross-react with another member, they will also exhibit antigenic differences depending on how closely related they are. Hence, it is possible that foods that have caused strong antibody responses which remain detectable even though they have not been eaten for years, do not cross react with other members of the same food family. Also, some antigens in foods are less able to initiate an immune response than others i.e. they are less immunogenic and, as a result, antibody production to them is less easily stimulated.


How does the food IgG ELISA test work?
ELISA stands for Enzyme Linked Immunosorbent Assay. ELISA is a standard diagnostic procedure used in hospitals for many tests such as detection of viruses, measurement of hormone levels etc. The food ELISA test measures antibodies to foods. These antibodies are also known as food immunoglobulins or food IgGs. The test consists of a microtitre plate coated with extracts of a number common foods (the number depends on the test that you are taking). Three test wells are used to calibrate the assay and to provide a positive control. A patient’s plasma is diluted and dispensed into the microtitre plate to allow any food IgGs to bind to the food extracts. The bound food IgGs are detected using an antibody to human IgGs that is linked to an enzyme. This antibody recognises the food IgGs and binds to them. Finally, a chemical solution is added which in the presence of the enzyme changes from colourless to blue. In this way, the food IgGs in the patient’s blood can be identified.


In the ELISA, how do we know that results over 12.5 U/ml should be avoided?
This value has been found after studying the results obtained from a large number of healthy individuals. Values greater than 12.5 U/ml are higher than those found in the general population and are treated as positive and should be eliminated from the diet.


What does U/ml mean?
U/ml stands for Units per millilitre and is a measure of the concentration. All of the positive results on the ELISA test report are expressed in U/ml to show the concentration of food antibodies in the blood.


Why do IgG levels stay high for so long?
See Clinical FAQs.


Why do we not test for sugar, alcohol etc?
Food IgG-based food intolerance is caused by proteins and the antibodies directed against them. Sugar and alcohol are not proteins.






Can IgG levels remain high even if not consuming any of that particular food? (i.e. for years?)
Antibody levels may remain detectable some several years after exposure. Because certain foods such as wheat, dairy and corn are widely used as additives in processed foods or cosmetics, IgG levels are more likely to persist in an individual who mistakenly presumes that such foods have been completely eliminated from the diet.


I have been told to eliminate ‘x’ from my diet, but have not eaten it for years, why do I have a high IgG reading?
This is because either a) you have been eating ‘x’ in other foods unbeknown to you, or b) you have been eating foods within the same food family and these are causing antibody production; c) antibodies stimulated by other foods ‘cross react’ with x in the test.


In that case, how do I know that the other results are not due to cross–reactivity?
They may be but to start with your nutritionist will recommend elimination of the food identified by the test………


Should I ignore these results then?
No. Ask your nutritionist to suggest which of the foods you do eat belong to the same food family as x and which might be stimulating antibody production. Your nutritionist may suggest that you eliminate these from your diet too.


Is it possible to have high IgG levels and not experience symptoms?Yes, some people do have high IgG levels to certain foods but do not have any symptoms at all. This is possibly due to their immune system being extremely efficient at clearing away the antigen-antibody complexes before they have chance to be deposited in the tissues and cause a problem.


Is there any evidence for complexes actually causing symptoms?
A study of infants with milk intolerance showed that symptoms appeared within hours of cow’s milk consumption and that this was accompanied by notable immune complexes appearing in the serum.


Surely even only one positive response indicates a leaky gut?
No, because food antibody responses occur naturally in the absence of increased gut permeability which is the hallmark of leaky gut


Does a Leaky Gut need to be repaired before those foods can be eaten again without symptoms?


If all food molecules get through, why do some lead to food intolerance and some not?
Two main factors govern the development of an IgG antibody-based food intolerance: the amount of a particular food in the diet and its ability to stimulate antibody production. Foods consumed in large quantities are more often associated with food antibody production, antigen-antibody complexes and symptoms. Some foods are more ‘immunogenic’ than others i.e. are more able to cause antibody production.


What determines which substances get through the leaky intestinal wall?
The composition of your diet and the size of the food particles. Also, minerals require carrier molecules which are often impaired in people with leaky gut. This can lead to mineral deficiencies in such individuals.


What is Leaky Gut Syndrome?
Leaky Gut Syndrome is a condition where large gaps develop between the cells of the intestinal wall causing large quantities of partially digested food to ‘leak’ into the bloodstream. The symptoms of Leaky Gut Syndrome are many and varied and include: abdominal pain, heartburn, insomnia, bloating, anxiety, gluten intolerance, malnutrition, muscle cramps and pains, poor exercise tolerance, food allergies.


Why do high IgG antibody levels cause symptoms?
When a food causes the body to produce high levels of IgG then these antibodies combine with the protein in the food to form an ‘antigen-antibody complex’. These complexes are usually eliminated by other cells in the immune system. However, if the immune system is overloaded, these insoluble molecules become deposited in various areas of the body, such as the head, lung tissue, gastro-intestinal tract, skin and joints where they produce symptoms such as headaches, asthma, irritable bowel syndrome, eczema and rashes, and arthritis.


How do we know that the complexes are deposited in certain areas? Intestinal biopsy studies have shown evidence of immune complexes in patients with cow’s milk sensitive colitis. Other studies have demonstrated deposition of human IgG and cow’s milk proteins in lung tissue specimens taken from infants with pulmonary hemosiderosis.





Once I have done a test what do I do next?
Once you have the results for your test, it is recommended that you consult a nutritionist, who will help you to understand the results and provide you with advice on dietary changes. You will be given a Dietary Support Booklet for further information that will help you understand what changes you will need to make. If you have your test done at our clinic we will explain the results to you, and give advice on how to safely make changes to your diet.


If I have had postal test done do I need to visit a nutritionist to discuss these results?
Once you have received you results, we advise you to see a nutritionist, who will advise you how to eliminate foods from your diet and which foods you should substitute to ensure that you do not result in any nutritional deficiencies. They may also offer support and encouragement with regular progress checks, as it can be quite a daunting task sticking to a new diet on your own. We also offer free 30 day email support via our website.


I have a lot of positive results, how do I cut out everything?
If you have a lot of positive results, it can be a very daunting task trying to cut out everything whilst maintaining a nutritionally well balanced diet. In these cases, we recommend you visit a nutritionist who will help you to avoid the foods with a strong positive response, and to rotate the foods with a lower positive result.


What does it mean if I have lots of positive results?
Potentially, you may have a condition known as ‘Leaky Gut’. You should consult a nutritionist who will be able to give you advice on how to deal with this condition.


Do I have to avoid these foods for the rest of my life?
No. Once you have avoided those foods for at least 3 months, and you have noticed an improvement in your symptoms, then you can start to gradually introduce the foods back into your diet. You should introduce one food at a time, with an interval of 4 days before trying another food. If you do not notice the return of any symptoms, then you can continue to include that food in your diet on an occasional basis. You may find a food and symptom diary useful whilst re-introducing foods.


How long do I have to avoid these foods?
It is recommended that you should avoid any food with a high IgG level for a minimum of 3 months. If you do not notice any improvement after this period of time, then you can assume that this food is not responsible for your symptoms.


If I avoid foods that show a high IgG reading, how long will it take before the IgG level returns to a normal level?
Over time, the concentration of IgG antibodies to that particular food will gradually decrease. The half life of IgG in the blood stream is approximately 23 days. However, antigens that have been stored in the liver may be slowly released over several months, resulting in some persistent antibody production. The levels, however, will decline gradually, barring any new exposure.


Do I have to eliminate that particular food completely from my diet in order to reduce my symptoms, or can I still have a little occasionally? The most effective course of action is to eliminate the food completely. As long as exposure is maintained, antibodies will continue to be produced and the immune system primed to react. Exposure to foods of the same food family should also be avoided.


I started to avoid foods from my diet, and now I feel a lot worse, is this normal?
This is a normal reaction for many people in the first few days after excluding a food or foods, due to ‘withdrawal-type’ symptoms. It is quite common to feel worse for a few days, but this phase soon passes and an improvement is usually noticed after a week or two.


Do I need to have a re-test after a few months?
Most people do not need to have a re-test, but if you would like another test we usually advise a period of 12 months in between tests. If your symptoms have improved and you have been able to successfully re-introduce the foods, then a re-test is unnecessary.


If I have been avoiding foods from my diet but would like them tested, how long should I introduce them before the test?
You should introduce a portion of these foods into your diet for at least 7 days before taking the blood sample. However, if you experience severe symptoms as a consequence, should immediately stop eating them and assume that you are still intolerant to them.


Why do I feel sometimes feel better after immediately eating a food that I am supposed to avoid?
Some people find that they feel better for a short while after eating foods to which they have high IgG levels. However, if they continue to eat those foods, the symptoms return. Eating more of the food once again brings relief, creating a vicious cycle of addiction that is difficult to break. This can be overcome by strictly eliminating the reactive food for a minimum of 3 months.


What is cola nut and what foods is it in?
Cola Nut is the seed kernel of a large African tree grown commercially around the world. It is extremely popular in the tropics as a caffeine containing stimulant. Key constituents are theobromine, caffeine, tannins and phenolics. It also contains phlobaphens, the antocyanin pigment kola red, betaine, protein and starch. Cola is ingested daily by millions as one of the main ingredients in cola soft drinks. It is also used in diet and “high-energy” products such as food bars and as a flavouring in alcoholic beverages, frozen dairy desserts, candy, baked goods, gelatins, and puddings.


Why does cola nut come up positive for many people?
Cola is ingested daily by millions as one of the main ingredients in cola soft drinks. It is also used in diet and “high-energy” products such as food bars and as a flavoring in alcoholic beverages, frozen dairy desserts, candy, baked goods, gelatins, and puddings.




What about my calcium levels if I cut out cow’s milk and dairy completely?
Please consult the CNS Dietary Support Guide, available online here. It is interesting to note that foods such as whitebait, almonds, soya flour, brazil nuts and spinach contain more calcium per 100mg than whole milk.


What alternatives are there to cow’s milk?
Please consult the CNS Dietary Support Guide, available online here.


What are the symptoms of lactose intolerance?
If the enzyme lactase is deficient, or low, then the ability to absorb lactose will be greatly reduced causing symptoms such as bloating, flatulence, diarrhoea and abdominal pain.


What is lactose intolerance?
Lactose intolerance is the inability to absorb lactose – the predominant sugar in milk – into the digestive system. If lactose is not absorbed properly, it ferments and this results in abdominal pain, a bloated stomach, stomach rumbling, increased wind and diarrhoea. Lactose is a disaccharide, which means that it is composed of two other sugars bound together. In order for lactose to be absorbed, it must be split into those two smaller sugars by an enzyme called lactase, which is present in the lining of the small intestine. If the levels of the lactase enzyme are low or absent, then that splitting does not occur and fermentation of the lactose occurs by bacteria in the large intestine. Lactase activity is high in babies and declines as the amount of milk in the diet decreases. Some people may have very low lactase levels but not have any symptoms. The reason for this is unknown. A lactose tolerance test, a hydrogen breath test, or a stool acidity test is required for a clinical diagnosis.


What are the main proteins in milk?
The total protein component of milk is composed of numerous specific proteins. The primary group of milk proteins are the caseins. All other proteins found in milk are grouped together under the name of whey proteins. The major whey proteins in cow milk are beta-lactoglobulin and alpha-lactalbumin.


If cow’s milk comes up positive, does that mean that I am lactose intolerant?
No. Lactose intolerance is the inability to digest lactose, the major sugar found in milk. It is caused by a shortage of the enzyme lactase, which is produced by the cells that line the small intestine. The food IgG intolerance test does not detect the lactase enzyme and therefore cannot diagnose lactose intolerance.



If I come up positive to wheat, does that mean I have Coeliac Disease? Coeliac disease is an intolerance to gluten that is found in wheat, rye and barley. It affects approximately 1 person in 1000 in the UK and is a life-long inflammatory condition of the intestinal tract. In our test gluten has to be isolated from the grains that contain it using alcohol extraction. Our wheat extract does not contain gluten but includes other proteins found in wheat that can be extracted using an aqueous solution. Therefore, a positive wheat result does not diagnose coeliac disease.


I have completely eliminated wheat from my diet for many months now, and after a re-test, my IgG levels are still high, why?
Over time, the concentration of IgG antibodies to that particular food will gradually decrease. The half life of IgG in the blood stream is approximately 23 days. However, antigens that have been held in the liver may be slowly released over several months, resulting in some persistent antibody production. The levels, however, will decline gradually, barring any new exposure.


I know that I have a reaction to wheat and have been avoiding it, but it did not show up in the test, why?
If you have been avoiding a particular food for a few months, it is possible that antibody levels to the food concerned have reduced to a level undetectable by the test.


Why has gluten come up positive but not wheat?
The wheat extract does not contain gluten but other proteins found in wheat such as seed storage proteins. The gluten extract does not contain these proteins but is a pure preparation of gluten. If you have antibodies to gluten but not to other proteins found in wheat, wheat will not show a positive result. Similarly, if you have antibodies to non-gluten proteins, wheat will show a positive result and in the absence of antibodies to gluten, gluten will remain negative.


What alternatives are there to wheat?
Please consult the CNS Dietary Support Guide, available from us by email.


What is durum wheat and why has that not come up positive, although wheat has?
Durum wheat and common wheat are different species of wheat. Durum wheat is very hard and is usually used to make flour and semolina for pasta. The protein content is different and therefore one can show up positive and not the other. Many people find that they can tolerate durum wheat if they are positive for wheat but negative to durum wheat.




If I come up positive to yeast, does this include brewers yeast?
Yes, the test includes both bakers and brewers yeast. If you come up positive to yeast, it is vital that you plan ahead as yeast is present in many different foods.


If the yeast comes up positive, does that mean I have Candidiasis?
No, not necessarily, the test just shows that you have an elevated level of antibodies to yeast in your body. If you would like to confirm whether you have Candidiasis, then we have a separate test for specific antibodies against the Candida albicans yeast.


What alcoholic drinks do not contain yeast?
All alcoholic drinks depend on yeasts to produce the alcohol, however distilling and filtering will tend to remove most of the yeast. Spirits, such as gin or vodka will have the lowest amount of yeast present compared with wines and beers.