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Food Allergies – are IgG tests useful?


More and more parents are coming to me with questions about food sensitivities. They wonder whether there is any real reason to take certain foods out of the diet; if foods might be causing their child's troubling symptoms like their aggression or their tantrums or their eczema.

They wonder about testing. They wonder about the dangers of restrictive diets.

The answer to what's contributing to your child's physical or mental/emotional symptoms is complex. But the piece I can fit in for you is the impact of food.

This particular blog post outlines where I stand on food sensitivities and food sensitivity testing. The short answer is, I don't find these tests all that useful, particularly as a first step. Read on for the explanation....

What's a Food Sensitivity?

Unlike a full blown allergy which can be obvious and is fairly straight forward for your doctor to test for, food sensitivities are tricky to tease out. Reactions can range from sleepiness to hyperactivity to skin rashes and tummy pain... anything, really, because food can influence every corner of our bodies.

It is estimated that 1 in 3 children suffers from a food sensitivity (also called an intolerance), and this issue seems to be on the rise. 

Food sensitivity happens when either the immune or nervous system mounts a hyper-response to certain foods or environmental stimuli.  Inflammatory chemicals are released and those can contribute to complex conditions such as asthma, ADHD, Autism, diabetes, celiac, and many more. For some kids, food sensitivity is a BIG contributor to their health issues and figuring this out yields great results. So food irritation remains one of the Four Pillars Of Resilient Health™ that I explore with my clients.

But the message I want to bring to you here is that food sensitivity is a symptom, not a diagnosis….

What is food sensitivity really?

Food sensitivity is a call to look deeper into the resilience of the body.

Let me explain by telling you about this interaction I had with a mom recently....

A mom of three approached me, interested in running a food sensitivity test for her son who was experiencing ADHD-like behaviour, dry patchy eczema-like skin, and interrupted sleep.

This blood test runs about $300 and tests for an IgG immune response to over 200 foods. This mom thought it might help her identify the root cause of her son’s troubles.

Now, the validity of this test is hotly debated. IgG antibodies are "memory" antibodies; they can be triggered simply because they have seen a food for a second time.

But on the other hand, an IgG test can be a helpful screening tool to see if any foods are eliciting an extreme response from the immune system. If there's an extreme IgG response, that would be a red flag indicating that particular foods could be contributing to inflammation and immune activation in the gut. It's not a diagnosis of an allergy, but it could be taken as a red flag pointing us towards a potential source of irritation and stress. In some cases we can use that information to construct a careful elimination-provocation diet to determine if these foods are, in fact, contributing to symptoms. 

For this mom, though, I told her that I did not think the IgG test was the right place to spend her money.

This mom had observed that when her son ate cheese and tomatoes he got lethargic and irritable. Those were trigger foods for him that were likely to come up positive should she run the test. But I explained to her that the problem was not actually the cheese and tomatoes; the problem was the body’s inability to tolerate them because of reduced resilience.  So that is where I suggested she focus her energy first, before testing... raising resilience.

I gave this mom a copy of my book, which outlines the 2-pronged approach and Core Dietary Strategies for boosting resilience, and suggested she work on those strategies first. At the same time she was to keep out the cheese and tomatoes, and any other food that was clearly causing noticeable symptoms.

At that point, after really working on raising resilience by following the strategies in the book (she actually decided to join my coaching program so she could get more support and guidance), if her son was still not tolerating cheese and tomatoes (or anything else) she could consider the test as a way to go deeper. I suggested that if she get to that point that she add on a test for zonulin, which is a protein that regulates the permeability of the gut lining. The combination of high IgG markers plus high zonulin is typically an indicator that there is more work to do on nourishing the digestive system. (NOTE: now, a few years later, we have the GI MAP test. I think this is a better option because it's more comprehensive and looks more deeply at function).

But the point is, there was work for her to do first. Until she had taken some basic steps to improve resilience I didn’t think it was worth shelling out the $300 for any test.

So here’s my take-home message about food sensitivities and IgG tests…

Food sensitivities are becoming more and more of a problem and there is no doubt in my mind that food irritation is worth exploring if your child is exhibiting troubling symptoms - be they physical or mental/emotional.

If left undetected food sensitivities can cause myriad symptoms that involve the skin, the bowel, the brain, behaviour, hormones…. just about every body system can be affected because the problem is not the food itself, it's the inflammation being triggered by the food.  

But while IgG tests can highlight foods to which the IgG arm of the immune system could be over-reacting and can help us construct an elimination diet to see if those foods are actually problematic, restricting a child's diet can be difficult and can open the door to nutritional deficiencies, so we have to be careful. The IgG test is not a diagnosis of an allergy, nor does it tell us much about the function of the gut; it is just a screening tool to help identify potential irritation.

But we have to ask, "why is food even causing irritation?" Food's supposed to nourish us and give us life and vitality. So what's up with all this irritation?

Food sensitivity is becoming more and more common as the physical resilience of our kids is deteriorating. Their digestive systems are less able to render foods hypoallergenic, their digestive linings are becoming irritated at a younger and younger age, and their immune systems are more likely to respond inappropriately. The result? Food sensitivities.

Why is this happening? Here are a few possible reasons...

  • Increased accumulation to environmental toxins is putting extra burden on our immune systems
  • nutritional deficiencies undermine chemical processes in the body
  • reduced diversity of gut bacteria due to antibiotics, sugar, stress and increased exposure to chemicals and pesticides weakens the digestive and immune systems
  • genetically modified food is interfering with digestive and immune response,
  • increased rate of cesarean births but kids at risk of developing a hyperimmune response by shifting the microbial balance in the gut

All of this can contribute to the rise of food sensitivities so it’s not that surprising that we are seeing more kids becoming sensitive to more foods. 

But the real key to managing food sensitivities is to address those things that are eroding resilience. When we do, we often see sensitivities resolve on their own without ever having to restrict foods.

If you do use the IgG food sensitivity test, use it as a guide to construct an elimination diet, not as a diagnosis of food allergy. And I suggest you consider it (or the GI MAP test) only after you have done what you can do to bolster your child's resilience.  

Ready For More?....

Click to this video post to learn more about the gut-allergy connection.

If you have a baby, keep in mind that sensitivities can be thwarted by paying close attention to gut bugs when starting solid foods. Click here for more info on that.



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Inflammatory symptoms, immune system and food intolerance: One cause – many symptoms.

About Jess Sherman, FDN-P, M.Ed, R.H.N

Jess is a Functional Diagnostic Nutrition® Practitioner, Registered Holistic Nutritionist™ and Family Health Educator specializing in brain health & resilience for kids. She is the author of Raising Resilience: Take the stress out of feeding your family & love your life, and the creator of The Resilience Roadmap™ - a systematic process to help parents help their kids feel and function better. Her book and online resources have helped families in 44 countries improve the lives of their children with learning differences, anxiety, ADHD, autism and mood disorders by helping them find hidden stressors and fit the food and feeding piece into their health puzzles. She is the 2019 recipient of the CSNNAA award for Clinical Excellence for her work helping families get healthier, and she continues to bring an understanding of the power of good nutrition to the mainstream conversation about children’s mental health, learning, and overall resilience through her blog, courses and as a  contributor to print and online magazines. You can reach Jess at 

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The content on this website and in the guides and courses offered here is meant to provide information so that parents can make informed decisions and discuss these issue with their health care teams. It is not intended as, nor should it be considered a substitute for professional medical advice, diagnosis, treatment, or individualized care.