Frequently Asked Questions

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 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 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 to 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 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?

The laboratory has a policy for a lower age limit on testing for IgG food antibodies not to recommend testing on children under the age of 2 years. This policy is based 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 related to the fact that the infant gut is more permeable than that of an adult coupled with immature mucosal immunity that is still in the learning and development stage. Antibody measurements in Coeliac Disease are comparable to food IgG measurements used in the food intolerance tests. 

Is there any medication that I should avoid when taking a food intolerance test, due to its potential effects upon the results?

We do not recommend having one of these tests if you are taking immunosuppressant medication, as they may have an impact upon the results. To be sure of an accurate result, the test should not be taken until you have stopped taking these medications for at least 4-6 weeks.

It is extremely important that you do not come off any prescription medication without medical supervision. Unmanaged change in drug dosage can result in extreme adverse consequences. Steroids (or corticoids) in particular should not be stopped without advice from a medical practitioner as they need to be reduced at a controlled rate.

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 specialist 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 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 a 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?

Although 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 the customer know. However, if you are ordering two tests we can test from one sample if you provide a full microvette.

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.

Can I upgrade my test to a larger food panel?

You can upgrade for up to a maximum of 4 weeks from the date that your first sample is received.

What are the sample requirements and test turnaround?

A pin-prick blood sample is required. Results are available within 10 working days.