IgG Food Intolerance Test in Singapore

What an IgG Result Can and Cannot Tell You

We would rather set this out plainly before you spend money on a panel than explain it afterwards.

Every major allergy body that has examined food-specific IgG testing has reached the same conclusion: it does not identify food allergy or food intolerance. The EAACI task force report, published in Allergy in 2008 and supported by the American Academy of Allergy, Asthma & Immunology, found that positive IgG4 results frequently occur in people with no symptoms at all, and that the antibody represents a physiological response to food exposure.

The Canadian Society of Allergy and Clinical Immunology put it more directly in 2012, describing food-specific IgG as a marker of exposure and tolerance to a food, and discouraging the practice of testing it to identify or predict adverse reactions to food.

So what does that leave? The laboratory measurement is sound — the panel reliably reports how much IgG is present. What it does not carry is a proven link between that figure and your symptoms. A raised IgG to a food is evidence you have eaten it, and a normal IgG does not rule out a reaction to it.

Some people still want the test done, and it is available here. What we will not do is hand you a report with fourteen foods highlighted and leave you to redesign your diet around it. The consultation before, and the review afterwards, are where the value sits.

Food Allergy, Food Intolerance and Food Sensitivity

These three terms get used interchangeably, which is part of why food testing is confusing. They describe different things.

Food allergy

An immune reaction, usually driven by IgE. It is fast — typically within minutes to two hours — reproducible, can be set off by a very small amount, and may involve the skin, airway or circulation. This is the category that can become an emergency, and it is investigated with specific IgE or skin prick testing.

Delayed reactions that are still allergic

That split is a useful rule of thumb rather than an absolute one. A small number of food reactions are immune-driven but not IgE-driven, so they are neither fast nor detectable by any antibody test. The clearest example is food protein-induced enterocolitis syndrome (FPIES), which mainly affects infants and young children: repeated vomiting one to four hours after a food — commonly cow’s milk, soy, rice or oat — sometimes with diarrhoea, pallor and lethargy, and occasionally severe enough to cause shock.

This is worth spelling out here, because delayed reactions centred on the gut are exactly the pattern IgG panels are marketed against. FPIES is a genuine allergy rather than an intolerance, and international consensus guidelines diagnose it clinically, from the pattern of reactions — no IgG or IgE test identifies it. Repeated vomiting hours after a particular food, especially in a child, warrants paediatric assessment rather than a food panel.

Food intolerance

Not an immune reaction at all. It is a digestive or metabolic problem — lactose intolerance from low lactase activity is the clearest example, and fermentable carbohydrates are another common cause of bloating and wind. Intolerance is usually dose-related, so a small amount may be tolerated where a large one is not. Symptoms stay in the gut and are uncomfortable rather than dangerous. Because no antibody drives it, no antibody test can diagnose it — including an IgG panel.

Food sensitivity

A loose, non-medical umbrella term covering anything that does not fit neatly into the first two. It has no agreed clinical definition, which is worth remembering when a test is marketed against it.

What the Test Involves

It starts with a consultation. A doctor takes the history — what happens, how long after eating, how consistently, and what else is going on — and advises whether an IgG panel answers your question, whether a different investigation fits better, or whether both are reasonable. That conversation is the part that determines whether the money is well spent.

If you go ahead, the sample is a single blood draw and takes a few minutes. Have nothing to eat or drink for at least 2 hours beforehand and avoid oily or fatty foods for at least 8 hours, since a fatty sample can interfere with analysis. Keep eating your normal diet in the days before — cutting foods out in advance changes what the panel sees. Antihistamines do not need to be stopped for a blood test.

Results take about 6 weeks. The report is emailed to you, and a doctor goes through it with you: which flagged foods line up with your symptom diary, which are simply the things you eat regularly, and what a sensible next step looks like. Appointments run 30 to 60 minutes.