Do Food Allergy Tests Actually Work? The Truth About IgE, IgG & Food Intolerance Tests

About this episode

"Food allergy" gets used as a catch-all term, but it isn't one thing. In Part 1 of this two-part series, Dr. Kash Gupta pulls apart the very different biological processes hiding behind that single label — IgE-mediated allergy, non-IgE-mediated allergy, and plain old food intolerance — and why mixing them up is exactly how people end up ordering the wrong test.

From there, the episode goes under the hood of what a standard blood test is actually measuring. Dr. Kash explains how serum-specific IgE testing works, why a positive result doesn't automatically mean a true allergy, and the base rate problem that makes blanket food allergy panels unreliable without a proper clinical history first.

The back half of the episode moves into more advanced diagnostics: Component Resolved Diagnostics — which narrows down cross-reactive proteins like those in peanuts — and the Basophil Activation Test, a specialist lab test that offers a more functional readout of allergy than standard IgE testing alone.

Key takeaways

• Why "allergy" isn't one mechanism — IgE-mediated, non-IgE-mediated, and intolerance are biologically distinct
• What serum-specific IgE blood tests actually measure, and why a positive result doesn't always mean a true allergy
• The base rate problem that makes blanket food allergy panels unreliable without a clinical history first
• How Component Resolved Diagnostics narrows down cross-reactive proteins, using peanut components as an example
• What the Basophil Activation Test is and why it can offer a more specific, functional readout than standard IgE testing

Episode timeline

1. 00:17Introduction
2. 00:46If You've Been Told to Use a Food Allergy Panel
3. 00:56Why This Confusion Matters
4. 01:12What the Episode Will Cover
5. 01:42Allergy Isn't One Thing
6. 02:11IgE-Mediated Food Allergy
7. 02:40When IgE Testing Helps
8. 03:10Non-IgE-Mediated Food Allergy
9. 03:38Food Intolerance
10. 04:07Choosing the Right Test
11. 04:16What Blood Tests Actually Measure
12. 04:47How Serum-Specific IgE Works
13. 05:09Sensitization vs True Allergy
14. 05:37The Base Rate Problem
15. 06:07History First, Then Targeted Testing
16. 06:26Component Resolved Diagnostics
17. 06:56Peanut Proteins and Cross-Reactivity
18. 07:25Why CRD Is a Refinement Tool
19. 07:35What the Basophil Activation Test Is
20. 08:03How BAT Works in the Lab
21. 08:32Flow Cytometry and Activation Markers
22. 09:02Functional Readout of Allergy
23. 09:32Why BAT Can Be More Specific
24. 09:58Specialist Lab Requirements