Food Allergy, Intolerance and Coeliac Disease Explained
Published 24 October 2026 · 4 min read
A food allergy, a food intolerance and coeliac disease are three different things, even though people often say they "can't eat gluten" or "can't have milk" for all of them. The difference matters because it decides how careful you need to be with food.
This article is a general overview. Diagnosis and treatment are always for a doctor to decide.
Food allergy
What it is: An immune reaction to a particular protein in a food. The body mistakenly treats it as dangerous.
How it shows: Typically quickly, often within minutes to a few hours of eating. It can mean rashes, itching, swelling, digestive trouble or shortness of breath. In severe cases anaphylaxis can occur, a life-threatening condition.
Good to know: Even a small amount of the allergen can be enough to cause a reaction. That is why cross-contamination matters with an allergy, for example a shared chopping board or frying oil.
Example: Allergy to peanuts, eggs or cow's milk.
Food intolerance
What it is: Difficulty digesting a particular substance. The immune system does not usually play the main role.
How it shows: Most often as bloating, abdominal pain, diarrhoea or constipation. Symptoms often depend on how much you eat, and they can appear later.
Example: lactose intolerance. The body does not have enough of the enzyme lactase, which breaks down milk sugar. It is not an allergy to milk protein. Some people with lactose intolerance can tolerate a small amount of dairy or lactose-free products, but this is individual.
Coeliac disease
What it is: A lifelong autoimmune disease. Gluten (a protein in wheat, rye and barley) triggers a reaction that damages the lining of the small intestine.
How it shows: Symptoms can be digestive, but also other (tiredness, iron deficiency, skin problems). Sometimes symptoms are subtle or absent.
Good to know:
- The treatment is a strict gluten-free diet. Even a small amount of gluten can do harm, even if you feel no symptoms.
- Do not start a gluten-free diet before you have been examined by a doctor. Going gluten-free before testing can distort the results.
- Coeliac disease is not the same as a wheat allergy. It also differs from non-coeliac gluten sensitivity, where the gut is not damaged.
Side by side
| Allergy | Intolerance | Coeliac disease | |
|---|---|---|---|
| What it is | Immune reaction to a protein | Problem digesting a substance | Autoimmune disease |
| Onset | Usually fast | Often slower | Ongoing, even without visible symptoms |
| Amount | A little may be enough | Often depends on the dose | Even a small amount of gluten does harm |
| Risk | Can be life-threatening | Unpleasant, usually not life-threatening | Long-term damage to the gut |
Why it matters in a restaurant
Staff often cannot tell whether you have a "preference", an intolerance or a serious allergy. So it pays to say it clearly:
- "I have coeliac disease. I need a completely gluten-free meal, with no cross-contamination."
- "I have a nut allergy. It is serious."
- "I have lactose intolerance. A small amount is fine for me."
You can find more on how to ask in How to ask about allergens in a restaurant.
If you suspect an allergy or coeliac disease, see a doctor. For acute symptoms such as shortness of breath or a swollen face, call the emergency number (112 in Slovakia and across the EU).
Frequently asked questions
What is the difference between a food allergy and a food intolerance?
An allergy is an immune reaction to a protein in food and can be life-threatening. An intolerance is a problem digesting a substance, usually with unpleasant but not life-threatening symptoms.
Is lactose intolerance the same as a milk allergy?
No. Lactose intolerance means the body lacks enough lactase to break down milk sugar. A milk allergy is an immune reaction to milk protein.
Is coeliac disease an allergy to wheat?
No. Coeliac disease is an autoimmune disease triggered by gluten, and it damages the small intestine. A wheat allergy is a different, immune reaction to wheat proteins.
Should I try a gluten-free diet if I suspect coeliac disease?
Not before you have been examined by a doctor. Going gluten-free before testing can distort the results.
Does a small amount of gluten matter with coeliac disease?
Yes. Even a small amount of gluten can do harm, even if you feel no symptoms.
Sources
- Husby S. et al.: European Society Paediatric Gastroenterology, Hepatology and Nutrition Guidelines for Diagnosing Coeliac Disease 2020. Journal of Pediatric Gastroenterology and Nutrition, 2020.
- Muraro A. et al.: EAACI Food Allergy and Anaphylaxis Guidelines. Allergy, 2014.
This information is general and does not replace medical advice. If you have an allergy, always check the ingredients with the staff.