Food Sensitivity vs Food Allergy vs Intolerance
Content last reviewed 2026-09-12 · Educational information — not medical advice
Quick answer
Three different biologies wearing similar names: ALLERGY = IgE immune reaction (potentially anaphylactic); INTOLERANCE = enzymatic failure (lactose); SENSITIVITY = poorly-defined IgG-mediated claims sold by unvalidated kits. Testing and consequences differ completely.
The taxonomy decoded
| Category | Mechanism | Onset | Testing | Severity ceiling |
|---|---|---|---|---|
| Allergy | IgE immediate hypersensitivity | minutes–2 hours | specific IgE (blood/skin) — validated | anaphylaxis/death |
| Intolerance | enzyme deficiency (lactase...) or pharmacological | 30min–hours, dose-dependent | hydrogen breath tests, genetic lactase; elimination trials | misery, never death |
| 'Sensitivity' (IgG) | proposed immune-complex theory | days claimed | IgG food panels — NO validation | unproven category |
The IgG kit problem stated plainly
Everyone eating foods develops IgG to them — IgG presence indicates EXPOSURE and normal immune function, possibly even ORAL TOLERANCE. Commercial panels charging $200-700 for 'sensitivity profiles' sell normal biology as pathology, triggering unnecessary restriction diets with genuine nutritional harm potential. Major allergy organizations formally warn against them.
Lactose intolerance done properly
The template for REAL intolerance workup: hydrogen-breath-test confirmation, or simply four-week dairy elimination with structured reintroduction noting symptom timing/dose-dependence. Enzyme supplements (Lactaid) transform management once confirmed.
Celiac sits apart deliberately
Not allergy, not intolerance — AUTOIMMUNE disease with validated serology (tTG-IgA) and serious consequences. Requires gluten-LOADING before testing. Suspected wheat problems deserve celiac rule-out BEFORE generic wheat-avoidance labels stick.
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Frequently asked questions
But my IgG kit results matched how I feel!
Elimination-diets alone also match how people feel — expectation and withdrawal effects are powerful. Only blinded re-challenge distinguishes signal from noise.
Is non-celiac gluten sensitivity real?
Possibly, controversially — but it's diagnosed by exclusion AFTER celiac/wheat-allergy rule-outs, never by internet quiz or IgG kit.