Allergy, Intolerance, or Sensitivity? Why It Matters Which
Three physiologically distinct problems that get described with the same vague language
"I think I'm sensitive to X" gets used to describe at least three genuinely different physiological problems, which matters because they have different mechanisms, different tests, and different correct responses.
| Category | Mechanism | Severity | How it's diagnosed |
|---|---|---|---|
| Allergy | Immune (typically IgE-mediated — triggered by IgE antibodies, the immune system's rapid-response allergy trigger)[67] | Mild to life-threatening (anaphylaxis), minutes to 2hrs | Skin prick, blood IgE, or supervised oral challenge |
| Intolerance | Non-immune, enzymatic/digestive (e.g. lactase deficiency)[68] | Unpleasant, not dangerous; dose-dependent | Hydrogen breath test |
| Self-reported sensitivity | Often misattributed — see note below | Real symptoms, uncertain trigger | Supervised elimination + reintroduction, not self-diagnosis |
Self-reported sensitivity is the hardest category because it's defined by what it isn't. A blinded trial in people confident they had non-coeliac gluten sensitivity found that once FODMAPs were controlled for, gluten itself produced no more symptoms than placebo[69] — the actual trigger is often a different wheat component, or another food eaten alongside it, not gluten. The symptoms are real; the self-identified cause frequently isn't, which matters because broad unsupervised elimination diets carry a real cost — nutrient gaps, unnecessary restriction, and sometimes the same anxiety-around-food risk flagged for calorie tracking — that a precise diagnosis avoids.