Food intolerance vs food allergy
The three things people are usually confusing
| Food allergy | Food intolerance | Celiac disease | |
|---|---|---|---|
| Mechanism | IgE immune response | Digestive or enzymatic; often dose-dependent | Autoimmune |
| Onset | Minutes, sometimes up to two hours | Often hours, sometimes the next day | Variable, often chronic and vague |
| Dose that matters | Traces | Usually a threshold; small amounts often fine | Traces |
| Can it be dangerous? | Yes, anaphylaxis can be fatal | No, though it can be thoroughly miserable | Not acutely, but long-term damage is real |
| Typical symptoms | Hives, swelling, wheeze, vomiting, collapse | Bloating, gas, pain, altered stools | Varied: gut symptoms, fatigue, anemia, more |
| Validated test | Specific IgE, skin prick | Only per-mechanism: breath tests for lactose, fructose | tTG-IgA serology, then biopsy |
| Management | Strict avoidance, emergency plan | Find your threshold; most people keep some | Strict lifelong gluten avoidance |
Why the distinction changes what you should do
Because intolerance has a threshold and allergy does not. Someone who is lactose intolerant usually digests some lactose without trouble; hard aged cheeses and butter contain very little, and many people manage milk in coffee while reacting to a glass of it. The right question is "how much can I have", and finding that number gets you most of your diet back.
For an IgE allergy that question does not exist. Trace contamination matters, the correct answer is strict avoidance, and the reaction can escalate unpredictably. Applying intolerance thinking to an allergy is dangerous, and applying allergy thinking to an intolerance is how people end up on unnecessarily narrow diets: cutting dairy entirely when the real limit was a large glass of milk.
The confusions worth naming
Milk allergy is not lactose intolerance
One is an immune reaction to milk protein, the other an enzyme shortfall for milk sugar. They share a food and nothing else. You can have either, or both.
Wheat allergy, celiac disease and non-celiac gluten sensitivity are three separate things
Wheat allergy is IgE-mediated. Celiac disease is autoimmune and needs serology while you are still eating gluten. Non-celiac gluten sensitivity is a diagnosis of exclusion with no validated test, and there is reasonable evidence that fructans, which are in wheat and also in onion and garlic, account for a share of what gets attributed to gluten. That is one reason bread and pasta often affect people differently.
"Food sensitivity" is a marketing term, not a diagnosis
It has no agreed clinical definition, which is precisely why it appears on the packaging of tests that would struggle to claim they diagnose either allergy or intolerance. What the tests actually measure.
If it is intolerance, the useful work is finding the threshold
Not whether a food is "bad" for you, but how much of it you can have and under what conditions, because tolerance varies with dose, with what else was in the meal, and with sleep and stress. That is a measurement problem: several separate exposures, compared against how often you get symptoms anyway. A single bad evening after a suspect food is very weak evidence, since symptoms fluctuate on their own.
Our free diary sheet is set up for this, and the reintroduction protocol is the structured version.
Minthe is a wellness and self-tracking tool, not a medical device. It does not diagnose or treat any condition and isn't a substitute for professional medical advice. If you have red-flag symptoms such as blood in your stool, unintentional weight loss, difficulty swallowing, persistent vomiting or a fever alongside gut symptoms, see a clinician rather than tracking them.
Sources
- Santos AF, et al. EAACI guidelines on the management of IgE-mediated food allergy. Allergy, 2025;80(1):14-36. PubMed
Frequently asked
What is the difference between a food allergy and a food intolerance?
A food allergy is an immune system reaction, mediated by IgE antibodies, that can escalate to anaphylaxis and be fatal. It is triggered by tiny amounts and comes on within minutes. A food intolerance is a digestive reaction, usually enzymatic or dose-dependent, that makes you feel unwell without being dangerous. Lactose intolerance is the classic example: you lack enough lactase to digest lactose, so it ferments in the colon. The immune system is not involved.
Can a food intolerance become an allergy?
They are separate mechanisms, so an intolerance does not turn into an allergy. You can have both to the same food, which causes plenty of confusion: someone can be allergic to milk protein and separately lactose intolerant, and those need entirely different management.
Is lactose intolerance an allergy?
No, and the distinction is practical rather than pedantic. Lactose intolerance is an enzyme shortfall and is dose-dependent, so most people can handle some lactose, and hard cheeses and butter are very low in it. A milk allergy is an immune reaction to milk protein where even trace amounts matter and strict avoidance is required. Treating an allergy like an intolerance is dangerous; treating an intolerance like an allergy means restricting far more than necessary.
Is celiac disease an allergy or an intolerance?
Neither. It is an autoimmune condition, in which gluten triggers the immune system to damage the lining of the small intestine. That is why it is the one thing in this area that genuinely requires complete lifelong avoidance rather than a tolerable dose, and why it must be excluded before you start attributing symptoms to intolerance. Testing requires that you are still eating gluten.
Which test do I need?
It follows from which one you have. Suspected allergy means specific IgE or skin prick testing with an allergist. Suspected lactose or fructose malabsorption means a hydrogen breath test. Suspected celiac means tTG-IgA serology while still eating gluten. There is no validated test for intolerance in general, which is why broad panels do not work. See our guide to food intolerance tests.