Food Sensitivity Testing: Does IgG Predict Intolerance?

Food Sensitivity Testing: Does IgG Predict Intolerance?

Food Sensitivity Testing: Does IgG Predict Intolerance?

Food sensitivity tests are a popular new way to look for the root cause of symptoms bloating, rash, and migraine. But do they work? What does the science say? Let’s take a deep dive into how they might work and what immunoglobulin G can really tell us.

What are Food Sensitivity Tests?

You may have seen them in ads online or on TV: companies promising that in just a few short weeks and with a few drops of blood, you can be free of all the foods that cause gut problems, rashes, and migraines. It sounds great, but it has a hefty price tag, and the science is shaky at best.

Food sensitivity or intolerance is a complicated topic with a lot of room for confusion.

We go back to the beginning and explore what food sensitivity is and how to find it in our previous two posts:

In this post, we’ll cover:

  • How “food sensitivity tests” are supposed to work,
  • Why they don’t work, and
  • How to actually find and address food sensitivity.

How is it Supposed to Work?

IgG food sensitivity tests assume that all IgG is pro-inflammatory. According to the companies that offer IgG food sensitivity tests, removing foods with “high IgG reactivity” is associated with reduced gastrointestinal, skin, and migraine symptoms. These are some big claims—what are they ?

Immunoglobulin G

So, foods cause inflammation and inflammatory symptoms. On that much, we agree with the companies that offer food sensitivity testing. Thus far, however, we haven’t touched on the biological marker than such companies use to find food sensitivities: IgG.

Immunoglobulin G, or IgG, is the most common antibody in your blood. Curiously, IgG can either promote or prevent inflammation depending on whether and which sugars are bound to it [1, 2, 3].

Pro-Inflammatory IgG

IgG attaches to pathogens and other foreign materials and helps your white blood cells pick their targets. Your body produces highly specific IgG and immune responses against pathogens that it has encountered before. That’s why you’re so unly to get diseases chickenpox more than once, for example [4, 5].

When IgG binds to a pathogen that it “recognizes,” white blood cells attack it, engulfing or killing it. As white blood cells arrive on the scene, they tend to produce inflammatory signals [4].

These steps are all part of a healthy immune response to a direct threat [4].

Anti-Inflammatory IgG

Researchers are still fleshing out their understanding of how binding to sugars changes IgG’s function. What we know is this: certain sugars act a switch that flips IgG from a pro-inflammatory to an anti-inflammatory molecule [6, 7].

Let’s back up: what role do sugars have? Which ones are anti-inflammatory?

The Role of Sugars

Multiple sugars can be bound to IgG, including fucose, galactose, and sialic acid. These change the function of the IgG molecule and send specific signals to immune cells [8, 9, 10, 11, 6].

When IgG is bound with fucose, it is said to be fucosylated. wise, IgG bound to galactose is galactosylated and IgG bound to sialic acid is sialylated.

Generally speaking, high fucosylation and low galactosylation and sialylation are associated with higher inflammation. That is, fucose bound to IgG tends to increase inflammation, while galactose and sialic acid tend to decrease it. The higher the ratio of fucose to the other two, the greater the inflammatory association, and vice versa [12].

Sialic acid can’t attach to IgG without a galactose molecule. When these two sugars are bound, the immune system tends to relax and stop responding to the IgG’s target antigen.

Thus, galactose and sialic acid protect against allergies and autoimmune disorders.

Human breast milk is extremely high in sialic acid, while red meat and dairy are the main dietary sources [12, 13, 14, 8, 15, 16].

Metabolism, Lifestyle & Sugar Binding

Various metabolic factors known to either increase or decrease inflammation also interact with the sugars bound to IgG.

CRP and interleukin-6 (IL-6) are signals that promote inflammation; they are associated with low sialic acid and galactose binding to IgG. High blood triglycerides and insulin have the same effect. HDLcholesterol, the “good” cholesterol that decreases inflammation, is associated with high sialic acid and galactose binding to IgG [12].

The direct relationship between lifestyle choices and sugar-bound IgG has not been well studied. However, the links between CRP, IL-6, cholesterol, triglycerides, insulin, and IgG status suggest that optimizing these metabolic markers could improve galactosylation and sialylation. Further research will paint a clearer picture [12].

Autoimmunity & Remission

In autoimmune disease, the immune system attacks an antigen in one of the body’s own tissues. For example, in rheumatoid arthritis, the immune system attacks the joint tissues and causes painful inflammation [13, 17].

Adults and children with rheumatoid and juvenile arthritis have significantly less galactose and sialic acid bound to their IgG. The same happens in people with Wegener’s granulomatosis, an autoimmune disease that causes inflammation and death of blood vessels [6, 18].

On top of that, more galactose and sialic acid bind to IgG during pregnancy. According to some researchers, this may be why some women with rheumatoid arthritis experience less pain or even disease remission while they are pregnant. Sialic acid then concentrates in breast milk, which protects breastfed babies from infections and helps them build a healthy gut flora [6, 19, 20].

Anti-inflammatory IgG increases tolerance; that is, it tells the body not to attack an antigen. Unsurprisingly, then, galactosylation and sialylation of IgG prevent tissue death and may cause some autoimmune diseases to go into remission [4, 13].

Predicting Tolerance in Allergies

People with allergies have IgE reactions to certain allergens, and they also tend to have high IgG against those same allergens. This is one of the reasons some people give for using IgG testing to find food sensitivities [21].

However, high IgG may actually predict the development of tolerance; that is, if you have high IgG against an allergen that triggers an IgE response, you’re more ly to outgrow that allergy later in life [22, 21, 14].

Anti-inflammatory IgG may block allergic reactions. The higher the ratio of IgG to IgE, the more ly we are to tolerate trigger foods over time [23].

IgG Takeaway

All this is to say that IgG is a complex molecule and that simply having high levels of IgG in your blood doesn’t mean you’ll have inflammation. Some IgG is anti-inflammatory; it tells your body not to attack.

Remember that antibodies, on the whole, tell your immune system that something is foreign, or not “self.” Galactosylated and sialylated IgG probably change that message a little bit, saying, “This is foreign, but it’s safe.”

Arguments in Favor of IgG-Based Elimination Diets

Some companies that offer IgG tests provide lists of studies that they say support the use of their product.

Such studies claim that eliminating IgG-reactive foods reduces symptoms of irritable bowel syndrome and improves stool quality. At least one study also found that people with Crohn’s disease have significantly higher levels of IgG [24, 25, 26].

Another study found that eliminating IgG-reactive foods reduced symptoms in two people with severe asthma [27].

Some studies have found a connection between IgG-reactive foods and the frequency and severity of migraines. The connection is not especially clear, however, and may be dependent on whether a person also has irritable bowel syndrome [28, 29].

One study found a correlation between IgG and depression. However, the subjects of this study also had increased zonulin expression; IgG was in no way confirmed as depression’s cause [30].

Many of the studies listed on the testing websites either suffer from design flaws or actually conclude that there is no significant link between IgG and intolerance. Many also assume that IgG is pro-inflammatory, with no mention of the anti-inflammatory function of IgG [31, 32, 33, 34].

Why Doesn’t Food Sensitivity Testing Work?

Several leading medical organizations (the European Academy of Allergy and Clinical Immunology, the Canadian Society of Allergy and Clinical Immunology, and the American Academy of Allergy, Asthma & Immunology) advise strongly against using IgG-based food sensitivity tests [35, 36, 37].

So, why do so many experts advise against IgG-based food sensitivity testing?

Everyone Has IgG Against Common Foods

Remember that the immune system produces antibodies when it encounters foreign materials. Food, as it happens, is a foreign material. Multiple studies have shown that people have IgG in their blood against foods that they commonly eat, and that IgG does not correlate to symptoms of intolerance [38, 35, 39, 40, 41].

In one study, more than 21,000 Chinese adults were tested for food-specific IgG. All of them had IgG against foods that they ate regularly. Quantities of IgG against specific foods did not correlate with symptoms from eating those foods, either [39].

As discussed above, IgG tends to indicate tolerance – not intolerance – to specific foods [23].

Commercial Tests Can’t Detect Anti-Inflammatory IgG

Commercial tests don’t (and probably can’t) distinguish between the pro-inflammatory and anti-inflammatory versions of these antibodies. As was the case with the Chinese study, your test results might come back with IgG against most or all of your staple foods, with no information about what kind of IgG it is [39].

Commercial Tests are Unreliable

Another huge problem with commercial tests is that they’re unreliable.

In science, one of the most important things about a given study is whether it can be reproduced: given the right materials, could I conduct the same experiment and get the same result? If yes, then the experiment has produced good, solid evidence. If not, then something is wrong [42].

Commercial IgG tests don’t even seem to be doing the same experiment, so to speak. In one case report, a researcher ordered multiple commercial tests for herself: each one told her to avoid different foods. Not a single food gave a positive result across all tests [41, 43].

This same researcher conducted her own tests later. She removed various foods from her diet and reintroduced them later, one by one, to see if they produced symptoms. Only four of the ten foods identified by the commercial tests produced measurable symptoms; she also experienced symptoms from foods not identified by any of the tests [43].

Is IgG Testing Ever Appropriate?

Some studies suggest that IgG testing may help people with migraines, inflammatory bowel disease, or celiac disease avoid inflammatory triggers.

However, most professionals warn that IgG testing should only be used as a last resort, after other types of tests have failed.

These tests should never be the only diagnostic tool employed, and the results of an IgG test should not take precedence over other tests [44, 45, 35].

Furthermore, avoiding foods IgG testing only appears to reduce the incidence of migraines in the short term. In one study, such an avoidance diet reduced the incidence of migraines after four weeks, but not after twelve weeks [45].

Elimination Diets vs. IgG Testing

We’ve established now that IgG testing is inconsistent and ineffective, but also that food sensitivities exist and should be addressed to increase the quality of life. How do we address them? Is there no lab test to help us?

Unfortunately, unless you have a true food allergy, it would seem that lab tests are expensive shortcuts that don’t provide much useful information. Elimination diets and “oral challenges” may be the best way to find out what’s really making us sick [46, 47].

In an elimination diet, we remove the suspected trigger food or substance from our diet for some time. We determine if our symptoms are gone, and then reintroduce the food to see if symptoms reappear or worsen [46, 47].

Elimination and oral challenge tests are time-consuming and often difficult to interpret; health professionals will sometimes guide the process. For example, they may instruct a patient to avoid wheat and conduct the oral challenge in a controlled clinical or hospital setting. The patient might receive wheat flour or a placebo, thereby reducing the risk of bias in the diagnosis [46].

The most reliable and effective way to conduct an elimination diet is with the guidance of a doctor or dietitian. You may wish to conduct your own elimination and oral challenge tests with some of the common dietary triggers, but be careful of your own biases. Try to keep an open mind throughout the process, and don’t draw conclusions until after the tests are complete.


IgE or IgG: How Blood Tests Show Food Allergies

Food Sensitivity Testing: Does IgG Predict Intolerance?

A few years ago, I was diagnosed with Grave’s Disease (hyperthyroidism); the toll it was taking on my health was pretty dramatic. I went from an energetic, outgoing, outdoors all the time girl to someone that was lethargic and tired from a constantly racing heart.

I choose to see a naturopathic to treat the condition, after a scary  initial consultation with a traditional doctor that included the phase, “radiate your thyroid.” Being a believer in holistic health and medicine, I knew that the naturopath was the way to go.

As part of my treatment, the doctor I worked with prescribed traditional medications to help regulate my T3 levels, but she also had me start a series of herbs, the nastiest tasting tea in the world, and vitamins.

Along with that, she also suggested we do allergy testing to see what foods could be triggering inflammation within my immune system. I laid down on the table, let her prick my finger and off my blood went for testing.

When the results came back, they confirmed that I was severely lactose intolerant (not a surprise, I have been since I was young), had moderate intolerances to gluten (again I suspected this) but the results also showed that I was highly reactive to almonds, avocados and eggs (something that had been my morning breakfast for five years). Along with the highly reactive sensitivities, also came lesser ones, including bananas, pineapple, corn, cabbage, peanuts, and a few other things that made eating the greatest challenge in the world (and I am already a very healthy eater).

So What Do You Do When The Foods You Love To Eat Are “Taken” Away From You?

With the results from my testing, I proceeded to take everything my diet that was on that list. No bananas, no avocados, no pineapples, no corn! With the change, my cooking became more creative, I prepared the majority of meals at home since I couldn’t safely eat out and I became a master of very costly “allergen free” cooking.

After a while, though cooking is still a passion of mine, I became tired of always worrying about food allergies and/or intolerances. Sometimes, you just want to venture out to your favorite restaurant and eat whatever appeals to you.

Because of this, I decided to investigate the allergy tests I was given because aside from dairy (lactose) and corn, I didn’t think my allergies or intolerances were as severe as what was being reported.

What Are Food Allergies?

Before you believe you’re allergic to something, I think you should understand what a food allergy actually is. According to the Mayo Clinic, a food allergy is a reaction that occurs in your immune system after you’ve eaten a certain food.

These foods can lead you to break into hives, develop itchiness or swelling in the throat, nose, mouth and airways or even lead to anaphylaxis (yes, food allergies can be life threatening).

 When it comes to a food allergy, almost 90 percent of all food allergies are related to eight foods: milk, soy, egg, wheat, peanut, tree nuts, fish, and shellfish.

What’s The Difference Between A Food Allergy and A Sensitivity (or Intolerance)?

According to the American Academy of Allergy, Asthma, and Immunology, a food allergy is a reaction to food proteins that you system can’t break down and results in severe reactions the ones listed above.

A food intolerance (also known as sensitivity) is related to an enzyme deficiency in your digestive tract that makes it hard to process a certain food, but it doesn’t lead to the severe outcomes that an allergy does.

We can be sensitive to foods, but not allergic to them.

How Do You Know If You Have Food Allergies?

There are a variety of ways to determine whether or not someone has food allergies or intolerances, including simple elimination diets, saliva, hair, skin and/or blood tests.

Two types of blood tests, IgE and IgG, are becoming more common for determining allergies as they are believed to provide the greater accuracy in finding food allergies and sensitivities.

IgE test can only be ordered by licensed health care providers, while others (usually IgG) can be ordered online and sent directly to your home and some you can only get from holistic practitioners.

Two Types of Blood Tests – IgE and IgG

When it comes to IgE and the IgG tests, there’s often a lot of confusion between the two.

With the IgE test, a clinician is measuring the immune system’s response to particular foods by measuring the allergy-related antibody known as immunoglobulin E (IgE), an antibody that attacks foreign proteins that produce an immediate allergic response. The antibodies travel to cells, causing allergic reactions in the skin, gastrointestinal tract and/or anaphylaxis.  

With the IgG test, a clinician is measuring Immunoglobulin G (IgG) antibodies, IgG antibodies are used to detect (predicting and/or serving as indicator) possible sensitivities or intolerances someone may have towards certain foods; they do not measure or produce immediate allergic responses.

According to the Food Allergy Institute, IgE antibodies occur in abnormally large quantities in people with allergies; IgE antibodies are the only true indicator of food allergies.

On the other hand, IgG antibodies can be found in people that have food allergies, but also in the general world population.

Experts believe that the production of IgG antibodies is a normal response to the food you’re eating on a regular basis.

Should You Get An IgG or an IgE Test To Determine Food Allergies?

If you think you have food allergies and something as simple as an elimination diet hasn’t helped you determine if something in your food may be causing issues, then see you doctor and have them refer you to allergist for IgE testing.

There’s a lot of controversy surrounding, IgG testing and most doctors in the believe that IgG testing is unreliable and that the results lack clinical utility.

In an interview with Vice Magazine, Robert Hamilton, a professor of medicine at Johns Hopkins University said:

There is no firm, peer reviewed data that verifies that IgG antibody is diagnostically useful. This type of food sensitivity test is essentially a bogus test. It doesn’t mean that you are sensitive or intolerant to certain foods, and it doesn’t mean you should avoid exposure to them, or avoid eating them.

The science behind the validity and reliability of IgG tests is solid, given the fact that results are “predictive” indicators, it makes it hard for them to be a credible tool for making changes in your diet eliminating foods. So if you think you’re allergic to foods, get an IgE test.

If You’re Not Allergic To It, Then You Can Probably Eat It

After personally having both the tests done and changing my food choices the results, I believe unless it’s proven you’re allergic to it (IgE), then you can probably eat it. My IgG tests indicated a large amount of food sensitivities, but if I look at what I was eating regularly at that time, most of those foods were staples in my diet.

In the last two months, I’ve reintroduced foods that the IgG test indicated I had problems with back into my diet, eating them once or twice a month. To be perfectly honest, I haven’t had noticeable effect with the exception of gluten, so I’m leaving it out.

And after three years of not having pineapples, bananas and avocados (and even cabbage!), I’m glad I’m adding them back!

In a society so caught up in “eating clean” and eating well, we are starting to suffer from too much deprivation simply because one study or doctor eludes to something that could cause problems with our health.

But think about it, why would you deprive yourself of nutrient dense, whole foods if you aren’t severely allergic to them? An avocado isn’t fast food.  If you’re not allergic or intolerant of it, then eat it (or eat it in moderation). Tamara Duker Freuman, M.S., R.D., C.D.N.

, makes a stellar point when she said, “People can’t keep up restrictive diets regardless of how they feel.

” Personally, I’m happy to have avocado for guacamole and pineapple in my smoothies — and no more avoiding real food that plays a key role in my already healthy diet that I haven’t been irrevocably proven I’m allergic to (I do mourn not being able to eat cheese daily).

Photo by ELEVATE from Pexels


CSACI Position statement on the testing of food-specific IgG

Food Sensitivity Testing: Does IgG Predict Intolerance?

1University of Alberta, Department of Pediatrics, Division of Allergy and Immunology, 903 College Plaza 8215-112 Street, Edmonton, AB, T6G 2C8, Canada

Find articles by Stuart Carr

2BC Children’s Hospital, Department of Pediatrics, Division of Allergy, Room 1C31B – 4480 Oak Street, Vancouver, BC, V6H 3 V4, Canada

Find articles by Edmond Chan

3Humber River Regional Hospital, Department of Pediatrics, Pediatric Allergy Clinic, Suite 103 – 2115 Finch Ave West, Toronto, ON, M3N 2 V6, Canada

Find articles by Elana Lavine

4University of Western Ontario, Department of Medicine, Division of Clinical Immunology and Allergy, South Street Campus 2064 – 375 South Street, London, ON, N6A 4 G5, Canada

Find articles by William Moote

1University of Alberta, Department of Pediatrics, Division of Allergy and Immunology, 903 College Plaza 8215-112 Street, Edmonton, AB, T6G 2C8, Canada

2BC Children’s Hospital, Department of Pediatrics, Division of Allergy, Room 1C31B – 4480 Oak Street, Vancouver, BC, V6H 3 V4, Canada

3Humber River Regional Hospital, Department of Pediatrics, Pediatric Allergy Clinic, Suite 103 – 2115 Finch Ave West, Toronto, ON, M3N 2 V6, Canada

4University of Western Ontario, Department of Medicine, Division of Clinical Immunology and Allergy, South Street Campus 2064 – 375 South Street, London, ON, N6A 4 G5, Canada

Corresponding author.

Stuart Carr: ac.atreblau@rrac.trauts; Edmond Chan: ac.cb.wc@5nahCE; Elana Lavine: ac.otnorotu@enival.e; William Moote: ac.owu@etoomd

Received 2012 Jun 20; Accepted 2012 Jun 20.

Copyright ©2012 Carr et al.; licensee BioMed Central Ltd.This is an Open Access article distributed under the terms of the Creative Commons Attribution License (, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

The Canadian Society of Allergy and Clinical Immunology (CSACI) is very concerned about the increased marketing of food-specific immunoglobulin G (IgG) testing towards the general public over the past few years, supposedly as a simple means by which to identify “food sensitivity”, food intolerance or food allergies. In the past, this unvalidated form of testing was usually offered by alternative or complementary health providers, but has now become more widely available with direct-to-consumer marketing through a nationwide chain of pharmacies.

There is no body of research that supports the use of this test to diagnose adverse reactions to food or to predict future adverse reactions.

The literature currently suggests that the presence of specific IgG to food is a marker of exposure and tolerance to food, as seen in those participating in oral immunotherapy studies. Hence, positive test results for food-specific IgG are to be expected in normal, healthy adults and children.

Furthermore, the inappropriate use of this test only increases the lihood of false diagnoses being made, resulting in unnecessary dietary restrictions and decreased quality of life.

The immediate expense of the test to individuals (see below for details on cost) will be compounded by the costs incurred by an already-overburdened health care system. Confused by the information provided by IgG testing, individuals are ly to request additional specialist referrals and investigations which would otherwise not be necessary.

Additionally, and perhaps of greater potential concern, a person with a true immunoglobulin E (IgE)-mediated food allergy, who is at significant risk for life-threatening anaphylaxis, may very well not have elevated levels of specific IgG to their particular allergen, and may be inappropriately advised to reintroduce this potentially deadly item into their diet.

As a result of these serious and growing concerns, the CSACI has elected to issue a formal statement supporting the opinions expressed by the American Academy of Allergy Asthma and Immunology (AAAAI) [1], and by the European Academy of Allergy and Clinical Immunology (EAACI) [2].

Both of these organizations warn about the inappropriate measurement of food-specific IgG or IgG4 to suggest the presence or potential of adverse reactions to food. Recent guidelines emphasize that such testing plays no role in the diagnosis of food allergy or intolerance [3].

A recent Canadian publication also elaborates similar concerns from the perspective of community allergy practice [4].

In addition to content of all of the above documents, the CSACI is very concerned about the following issues:

1. The testing process is widely available in Canada, through a variety of complementary health providers, paramedical clinics, and some physicians.

2. A testing kit product is being sold directly to customers, in pharmacies.

3. Marketing strategies for the testing have included the placing of promotional materials in the waiting rooms of physicians without their knowledge or consent.

4. The price of the testing is often in the $400-$700 range, and some third-party payers offer reimbursement despite a clear lack of supporting evidence.

5. The test is also being marketed to concerned parents, and may lead to exclusion diets which carry risks of poor growth and malnutrition for their children: for example, the elimination of dairy products, wheat, eggs, and/or other foods found in healthy balanced diets.

The CSACI does not support the decision of licensed physicians and our pharmacist colleagues to offer such testing, given the overwhelming consensus against the validity of such tests.

The CSACI strongly discourages the practice of food-specific IgG testing for the purposes of identifying or predicting adverse reactions to food.

We also wish to remind the medical community that blood testing of any kind cannot substitute for consultation with a trained and accredited medical professional such as an Allergist/Immunologist for the diagnosis and management of adverse reactions to food.

The authors declare that they have no competing interests.

This Position Statement was the product of an ad hoc committee of the Canadian Society of Allergy and Clinical Immunology. Each of the credited authors contributed substantially throughout the planning, drafting and revision stages of the document, and all authors read and approved the final manuscript.

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What you need to know about food sensitivities

Food Sensitivity Testing: Does IgG Predict Intolerance?

Food sensitivities are blamed for everything from irritable bowel syndrome to mood disorders. And many of us are on special diets as a result – 6 per cent of Canadians, for example, believe they have non-celiac gluten sensitivity, according to the Canadian Celiac Association.

“There are so many symptoms and difficulties that are very hard to diagnose and treat, and people want answers,” says Wendy Busse, a registered dietitian in Red Deer, Alta., who specializes in allergies. Food-sensitivity tests are a popular starting point – but experts caution they're not ly to give you useful information. Here's why.

What is a food sensitivity?

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Food sensitivities are often confused with allergies, says Linda Kirste, a dietitian with HealthLink BC who focuses on food allergies. But an allergy is a specific response that involves the immune system – such as the anaphylactic reaction you'd get with a peanut allergy.

Food sensitivity, on the other hand, is a very broad term that includes most negative responses to food, including irritable bowel syndrome, migraines and weight gain. Mainstream medicine prefers to discuss food intolerance, which causes mostly digestive problems and isn't related to the immune system.

Are there tests for it?

IgG tests are marketed as a way of testing for food sensitivities. Most people order the blood tests, which cost hundreds of dollars, through naturopaths. The tests look for IgG antibodies – proteins created by the immune system – for more than 100 foods, ranging from dairy to seafood to specific spices.

Do these tests work?

The tests do measure IgG levels – but the idea that IgG levels are tied to food sensitivities isn't supported by the science. In fact, studies that looked at reducing allergic reactions in children for things such as milk or peanuts, researchers found that IgG levels went up as the severity of allergic reactions decreased. So it's actually seen as a sign a food is well tolerated.

Researchers believe that we produce the most IgG antibodies to foods that we eat regularly. “It's getting a constant booster shot,” says Stuart Carr, a pediatric allergist in Edmonton. That's why common foods, such as dairy, wheat and egg will often show up positive on an IgG test.

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Carr authored a 2012 position statement for the Canadian Society of Allergy and Clinical Immunology that concludes there is no research supporting using IgG tests to diagnose or predict adverse reactions to food. Previous statements from the American Academy of Allergy Asthma and Immunology and the European Academy of Allergy and Clinical Immunology agreed.

What's the harm?

If IgG tests don't work, there's the obvious concern that they're a waste of time and money. Dietitians also worry that the tests could lead to poor nutrition. That's especially important in children.

Research shows kids who have had their diets limited by food allergies can be susceptible to poor growth and to nutrient deficiencies, and restricting a child's diet due to suspected intolerances or sensitivities could have the same effect.

In extreme cases, it can result in malnutrition.

More commonly, it can contribute to an unhealthy relationship with food. “We have an opportunity as parents to support children developing a healthy relationship with food and eating,” says Kirste. Disrupting that could lead to unhealthy eating patterns, and increase their risk of kids developing eating disorders.

Are there other options?

For people who are worried they might have an issue stemming from certain foods, there's a better (and cheaper) way to find out: Try an elimination diet, under the guidance of a health-care provider.

“You keep a food diary for four to six weeks, and write down whatever symptom you're worried about,” Carr says. “If you identify a food or two from that, you take it the diet for two or three weeks, see if those symptoms improve.

You can sort out almost any food intolerance with a little bit of detective work.”

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It's also important to keep in mind that the problem might not be food-related at all. With all the buzz around restricted diets, it's tempting to think a sensitivity is behind a wide range of issues, and that's not always the case. “There is a tendency to want to blame food,” Busse says. “But I think it should be innocent until proven guilty.”

A version of this story first appeared in Healthy Debate, an online publication guided by health-care professionals and patients that covers health policy and evidence-based medicine in Canada.


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Food Sensitivity Testing: Does IgG Predict Intolerance?

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