Does IgG Intolerance Testing Work?

You may be wondering “should I get an IgG intolerance test?” On Instagram @AndreaHardyRD, I talk all about IgG testing and whether or not it’s something you might want to consider.

I am SO grateful for all the people that message me and say ‘I’m not so sure about this IgG intolerance test… does it work?’⁠
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Because that’s one more person I can save from a GIANT.WASTE.OF.MONEY.⁠
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Let me explain this as simply as I know how (thank you to Dr. Armin Alaedini for all the conversations we’ve had about the immune system and helping with the info below) I’m about to get REALLY science-y so hold on to your nerd glasses! 🤓⁠
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1) IgG can be a marker of immune recognition. When you digest and absorb food, your immune system has to recognize components (antigens) as safe. IgG plays a role in that. IgG is ALSO important in clearing pathogens (which dietary antigens can be recognized as) but this is a normal, healthy response to foods that are more ‘antigenic’. Guess which foods are more antigenic? Wheat, milk, eggs, soy – really any top 10 priority allergen. Guess what’s ‘red’ on most tests? You guessed it, more antigenic foods.⁠
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2) These tests talk about IgG as 1 molecule, but there are actually sub-classes of IgG. In fact, in studies on celiac disease versus non celiac wheat sensitivity, different IgG subclass responses, in combination with other immune markers may help one day to be a diagnostic marker. The important thing here to note is: a) The IgG subclass matters, and b) different responses occur with different conditions therefore EACH condition will need to go through rigorous testing and may require additional biomarkers to have utility.⁠
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3) These commercial tests measure total IgG. Which is not relevant in the context of diagnosing intolerances – as explained above. For example, IgG4 is associated with immune tolerance – if you pool it all together with the other subclasses, could you draw any relevance from it? No. (and even if you split it out at this point, it’s still not validated… so there’s that.)⁠
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OK I know this is A.LOT. Key takeaways. IgG is not a marker of intolerance. It does not give you ‘clues’ into your immune system function. Definitely, definitely, skip this test.