Allergy vs Intolerance
Northway Clinic in Canning Town, London offers a wide range of food allergy and food intolerance tests.
The specific terms food allergy, hypersensitivity and intolerance are all commonly used interchangeably, with some evident confusion regarding the actual difference between them.
Essentially, these terms all relate to an adverse physiological response to a particular food; however, the mechanisms by which this occurs are very specific to the individual type of food sensitivity in question. These reactions can be categorised as either immunological (IgE or IgG mediated) or non-immunological in nature and can initiate an immediate (minutes to hours) or delayed (several hours to days) response to a particular food. Identifying the specific reactive mechanism triggered by the ingestion of this food is vital to understanding the management and implementation of appropriate dietary interventions to limit potentially unpleasant (and in some cases, life threatening) symptoms.
IgE food allergy
Type I immediate IgE hypersensitivity immune response is more commonly known as a food allergy and this reaction typically occurs very quickly (within minutes to hours) after eating an offending food, with symptoms ranging from mild to severe.
Many are aware of food allergies causing anaphylaxis (the most common example being peanuts), but they may also experience itchy lips/tongue/throat, stuffy nose, headaches, stomach pain, diarrhoea, gas, bloating, skin reactions, and sudden fatigue.
Most people often know their ‘trigger foods’ because when the reaction occurs, it is so quick and happens soon after eating food. However, sometimes it isn’t always obvious, particularly with people who have multiple allergies. In these instances testing can be very useful and is done by measuring specific IgE antibodies in the blood to the suspected foods and food panels.
IgE allergy is tested by specialised tests and will not be identified by our IgG mediated food intolerance tests. If an individual suspects that they may have an IgE allergy, then they should consult one of our private GP to be tested for this.
Genetically inherited food intolerance
Classic food intolerances are known as non-immune mediated reactions. This means that, unlike IgG food intolerance or a classic allergy reaction, that the immune system is not involved. Some examples of this type of intolerance include enzyme deficiencies, such as lactose intolerance and histamine intolerance. Both of these intolerances are caused by the absence of the enzymes lactase and diamine oxidase (DAO) respectively.
Taking lactose intolerance as an example, lactase, normally secreted in the small intestine, is not produced which means that lactose (the primary sugar in milk) cannot be metabolized into its absorbable component monosaccharides, glucose and galactose. Undigested lactose cannot therefore be absorbed across the small intestinal epithelium and as a result, passes into the colon, where gut bacteria metabolize it into carbon dioxide, hydrogen and water. The characteristic symptoms of lactose intolerance are bloating, flatulence, abdominal cramping, and diarrhoea.
Lactose intolerance is tested by a specialised test and will not be identified by our IgG mediated food intolerance tests. If an individual suspects that they may have lactose intolerance, then they should consult one of our private GP to be tested for this.
IgG food intolerance
While IgE antibodies are responsible for acute allergic reactions, IgG-mediated manifestations take much longer to develop. IgG antibodies play a significant role in the shaping of the body’s normal immune.
The binding of IgG antibodies with a bacterial or viral antigen, results in antigen coating and the formation of an immune complex. This consequently triggers further immune responses, including the release of pro-inflammatory cytokines, with the developing inflammation being accompanied by mechanical damage to the surrounding tissues.
The activity of IgG antibodies is identical as far as food antigens are concerned. As the food components in patients with increased intestinal permeability (leaky gut syndrome) enter the bloodstream from the intestinal lumen on a continuous basis, the immune mechanisms undergo constant activation. This can eventually overload the immune system’s ability to clear such complexes efficiently, which results in chronic inflammation.
Elevated levels of IgG antibodies to food antigens have been observed in diseases associated with increased intestinal barrier dysfunction; in particular, IgA deficiency, coeliac disease and inflammatory bowel disease. The controversy surrounding food IgG testing relates to the significance of food IgG antibodies in the pathogenesis and diagnosis of food intolerance and a number of chronic illnesses, including IBD, IBS, migraine and arthritis. However, a number of clinical studies to date, have in fact been supportive of a role for food IgG testing in certain illnesses.
The clinical manifestations of chronic IgG-mediated reactions are determined by the target tissue or organ to which the immune complexes composed of IgG antibodies and the specific food antigens are transported within the bloodstream. High levels of the complexes accompany such dissimilar disease entities as migraine, irritable bowel syndrome, chronic fatigue syndrome and Crohn’s disease. The protective nature of IgG antibodies becomes a property that severely burdens and disturbs the body’s homoeostasis. This type of hypersensitivity is the so-called delayed allergy or food intolerance. The signs and symptoms develop within 8–72hrs after ingesting of the offending food.
Often, patients do not associate a given symptom with the food they eat, especially because of the lack of the characteristic “allergic” symptoms. This is the fundamental argument that highlights the controversial nature of this type III food allergy.
FoodPrint 200+ Food intolerance test
Northway Clinic’s FoodPrint test uses specific food extracts to identify the corresponding level of circulating IgG antibodies to these potential antigens and can therefore detect foods to which the immune system is reacting. This can help to guide individuals towards making informed dietary changes, in order to potentially alleviate unpleasant symptoms that they may be experiencing as a result of an IgG-mediated food intolerance.
FoodPrint 200+ is our most comprehensive food sensitivity test. The CNS FoodPrint® 200+ service utilises state of the art immunoassay microarray technology to detect food-specific IgG antibodies to 220 different foods. The full list of food items tested can be found HERE.
To perform this test the laboratory will require your blood sample. A finger-prick blood sample can be obtained with a help of a nurse at our London clinic (free of charge). Alternatively, a self-administered testing kit can be posted to your home address with a pre-paid return envelope. You can purchase the FoodPrint 200+ test below.
Blood Collection Procedure Video
Frequently Asked Questions
What are the sample requirements and test turnaround?
A pin-prick blood sample is required. Results are available within 10 working days.
What is an IgG?
IgG stands for Immunoglobulin (type G). Immunoglobulins are a class of proteins that function as antibodies 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.
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 IgG antibodies to these foods.
Do high IgG antibody levels cause symptoms?
When 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 tissues within the body, causing chronic inflammation and the subsequent production of symptoms.
Is it possible to have high IgG levels and not experience symptoms?
Yes, some people do have high IgG levels in certain foods but do not have any symptoms at all. This is most likely due to their immune system being extremely efficient at clearing away the antigen-antibody complexes before they have a chance to be deposited in the tissues and cause a problem. While it is true that certain common foods are more likely to show a positive result e.g. wheat, dairy, soya. The reason for this is that these foods are consumed on a regular basis in our diet and along with digestive issues this can increase the likelihood that the body may react to them. While an elimination diet will always be the gold standard, the benefit of doing a food intolerance test is that it will be able to quickly show which of the foods that are eaten on a regular basis, are a potential problem. In addition, the tests are able to highlight more unusual foods which a person may not have considered removing from their diet.
Why test for IgG antibodies to foods?
The efficacy of a diet based on the measurement of IgG antibodies specific for food components has been demonstrated in a number of conditions, both in independent studies and clinical practice. Excellent results have been obtained in patients with migraine, IBS and obesity.
Can I take the test if I am pregnant?
A food intolerance test is not recommended during pregnancy as the immune system is suppressed. However, 4-6 weeks after giving birth should be ok.
What is the lower age limit for testing?
Our testing partner Cambridge Nutritional Sciences (CNS) has an existing policy for a lower age limit on testing for IgG food antibodies is that we do not recommend testing on children under the age of 2 years. We base this on the European Society for Paediatric Gastroenterology, Hepatology, and Nutrition Guidelines for the Diagnosis of Coeliac Disease 2012, which states that there is a possibility of false-negative results occurring in infants younger than 2 years of age. This is related to the fact that the infant’s gut is more permeable than that of an adult coupled with immature mucosal immunity that is still in the learning and development stage. They have used this criterion as antibody measurements in Coeliac Disease are comparable to food IgG measurements used in our food intolerance tests. However, test providers are aware that there are in fact no published guidelines that specifically indicate a minimum age for testing for such IgG antibodies, for example, the guidelines for testing for coeliac antibodies indicate that such testing can be performed any time after the introduction of gluten into the diet. Therefore, where such requests are received from a statutory regulated professional the decision of when and what tests to perform will remain the responsibility of the requesting clinician. It is always worth consulting with our nutritionist or private GP.
Is there any medication that I should avoid when taking a food intolerance test, due to its potential effects upon the results?
Customers should avoid the use of immunosuppressant medication if possible if performing these tests, as they may have an impact upon the results. It is always worth consulting with our nutritionist or private GP.
How does the test work?
Food extracts are ‘printed’ onto nitrocellulose ‘pads’™ on a glass microscope slide, together with calibration standards and controls. A blood sample provided by the patient is diluted and dispensed onto each printed microarray. Food IgG antibodies, if present, bind to the food extracts and the results are measured by a high-resolution scanner, before being calibrated against the standards using the FoodPrint reporting software to give quantitative results. This software then produces a tailor-made printout of the final food IgG antibody result for each food on the requested food panel.
Do you need to re-introduce foods before taking a FoodPrint test – if so, how long for?
In general, we recommend that you follow your normal diet, so that the test will reflect what you usually eat. However, if you have specifically avoided food for more than three months e.g. cow’s milk, which used to be part of your normal diet and you would like it tested, we would recommend it is reintroduced. The recommendations are to reintroduce the food for 1 week eating a normal portion of that food at least once daily before taking your blood sample. If symptoms occur once the food is re-introduced, we recommend that you discontinue that food and conclude you are still intolerant to it.
Do I have to fill the microvette all the way to the white line?
If you are collecting a blood sample yourself, it is advisable to completely fill the tube, a half-filled microvette tube should be enough to run the test. If there are any problems with a sample the lab will let you know.
Do you need to store the blood in the fridge if not sending the same day?
Yes, it does need to be stored in the fridge with the lid secured if not sending on the same day.
Does the FoodPrint test for all subclasses of IgG antibody or only IgG4?
FoodPrint screens for all IgG subclasses 1-4, with the numbers on the test report representing the total IgG concentration for each food extract in the selected panel.
Where can I see a sample report?
A sample report can be viewed HERE
