Question 1

What is the test method?

Accepted Answer

Our food intolerance tests are done using a blood based method covering IgG 1,2,3,4, the blood sample collection process is done via a pin prick to the finger, it takes around 4-5 large droplets.

Question 2

Why do food cause an IgGantibodies response?

Accepted Answer

Generally, foods are broken down during digestion into their component parts e.g. amino acids, glycerides etc. These pass harmlessly through the gut as the gut becomes inflamed (bloated) these proteins enter the bloodstream. This is where they are recognized by the immune system as being ‘foreign’. The immune system responds by making IgG antibodies to these foods.

Question 3

What is the difference between hair and blood based test?

Accepted Answer

You can't test immune reactions via a hair sample, and in many cases there have been discrepancies in results when parts of the hair have been coloured/bleached. This has led to inconsistency in the sample tested twice. Our IgG 1,2,3,4 blood based testing covers the full range of antibodies responses, this is important, if a particular food elevates any antibodies against it, this means your gut and immune system recognises that food as a threat. This could affect the nutrients absorbed from this particular food and leads to multiple symptoms.

Question 4

Do high IgG antibody levels cause symptoms?

Accepted Answer

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.

Question 5

Why test for IgG antibodies to foods?

Accepted Answer

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.

Question 6

What is the lower age limit for testing?

Accepted Answer

Supply Life's 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 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. We have used this criterion as antibody measurements in Coeliac Disease are comparable to food IgG measurements used in our food intolerance tests. However, we 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.

Question 7

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

Accepted Answer

Customers should avoid the use of immunosuppressant medication if possible if performing these tests, as they may have an impact upon the results. Please refer to the medication datasheet in the “Support” section for further details.

Question 8

How does the test work?

Accepted Answer

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 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.

Question 9

Do you need to full the microvette all the way to the white line?

Accepted Answer

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 and 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.

Question 10

Do you need to store the blood in the fridge, if not sending the same day?

Accepted Answer

Yes, it does need to be stored in the fridge with the lid secured if not sending on the same day.

Question 11

Can I upgrade my test to a larger food panel?

Accepted Answer

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

Question 12

What are the sample requirements and test turnaround?

Accepted Answer

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

Question 13

Does the Supply Life test for all subclasses of IgG antibody or only IgG4?

Accepted Answer

Our process 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.

Study	Condition	Participants	Study Type	Duration	What improved	Evidence Strength
Singh et al. 2025 IBS IgG trial	IBS	223	Randomised, double-blind, sham-controlled	8 weeks	More people achieved ≥30% reduction in abdominal pain vs control	🟢 Strong
Atkinson et al. 2004 IBS IgG trial	IBS	150	Randomised, double-blind, sham-controlled	12 weeks	~10% greater symptom improvement vs control, up to 2× greater with adherence	🟢 Strong
Ostrowska et al. 2021 IgG vs FODMAP IBS study	IBS	73	Comparative (IgG vs FODMAP vs control)	8 weeks	Greater symptom and QoL improvement vs FODMAP and control	🟡 Moderate
Alpay et al. 2010 migraine IgG trial	Migraine	30	Double-blind, cross-over	6 + 6 weeks	Fewer migraine attacks and headache days	🟢 Strong
Zhao et al. 2025 migraine IgG cytokine study	Migraine	60	Controlled intervention	12 weeks	Fewer migraines + reduced IL-6, TNF-α, CGRP	🟡 Moderate
Bentz et al. 2010 Crohn's IgG trial	Crohn's disease	40	Double-blind, cross-over	6 + 6 weeks	Reduced digestive symptoms vs control	🟡 Moderate
Maiprasert et al. 2024 acne IgG RCT	Acne	75	Randomised controlled trial	12 weeks	Reduced acne severity (~33% in examples)	🟢 Strong
Kostić-Vučićević et al. 2017 Med Sport study	Athletes / wellbeing	22	Pilot (no control)	3 months	~40% reduction in indigestion, improved recovery	🔵 Early
Hardman and Hart 2007 IgG survey study	Mixed chronic symptoms	5,286	Observational survey	3 months	~72–76% reported symptom improvement	🔵 Early

All Studies

How to read this table

Key patterns across studies

1. Consistent symptom improvement

2. Strongest evidence in IBS and migraine

3. Personalised diets outperform general approaches

4. Evidence of biological effect

Explore individual studies

Unlock your full potential today

Get your easy to use food intolerance test today

Discover Products

Read more from the Intolerance Hub

Onion Intolerance