Food Intolerance: Common Questions
A reproducible adverse reaction to a food that does not involve the immune system.
Last revised
Food Intolerance: the questions people actually ask, answered from published guidance.
Key takeaways
- Not the same as allergy: intolerance does not involve IgE or anaphylaxis
- Commonest example: lactose intolerance
- Most useful single change: Keep a detailed food and symptom diary before excluding anything.
- Commonest mistake: Commercial IgG or hair-analysis food tests.
- See a doctor if any of the signs under "When to get help" below apply to you.
What is Food Intolerance?
A reproducible adverse reaction to a food that does not involve the immune system.
Why does it matter?
It is frequently confused with allergy, which is a different mechanism with a different level of danger, and with tests that do not work.
Not the same as allergy for Food Intolerance?
Intolerance does not involve IgE or anaphylaxis.
Commonest example for Food Intolerance?
Lactose intolerance.
IgG food tests for Food Intolerance?
Not recommended; they do not diagnose intolerance.
What is the single most useful thing to do?
Keep a detailed food and symptom diary before excluding anything.
What is the most common mistake?
Commercial IgG or hair-analysis food tests.
When should I see a doctor?
Call 999 for swelling of the lips, tongue or throat, difficulty breathing or swallowing, a widespread rash with faintness, or collapse after eating — that is anaphylaxis, not intolerance, and needs adrenaline immediately. See a GP for persistent diarrhoea, weight loss or blood in the stool rather than assuming intolerance.
Where to go next
- Myths About Food Intolerance, Checked Against the Guidance
- Starting Out With Food Intolerance
- Food Intolerance — the reference entry
- What the Guidance Really Says About Probiotics
- The Evidence on Liver Health, Without the Hype
When to get help
Call 999 for swelling of the lips, tongue or throat, difficulty breathing or swallowing, a widespread rash with faintness, or collapse after eating — that is anaphylaxis, not intolerance, and needs adrenaline immediately. See a GP for persistent diarrhoea, weight loss or blood in the stool rather than assuming intolerance.
Where this comes from
- NICE — Food allergy in under 19s
- British Dietetic Association — food allergy and intolerance
How this page was put together
Every figure, recommendation and warning above is taken from the guidance named in Where this comes from. Nothing on this page is inferred, summarised or generalised beyond what those bodies publish: where they give a number, it is their number, and where they are silent, so are we. Pages are rebuilt whenever the underlying record changes. Sign-off by a named clinician, where it has happened, is shown at the top of the page along with the date.
Medical disclaimer
This article is general information, not medical advice. It cannot account for your own history, medication or circumstances. Always speak to a GP, pharmacist or another qualified health professional before making changes that affect your treatment, and never delay seeking medical advice because of something you have read here. In an emergency, call 999.
