Is lactose intolerance the same as a milk allergy?

No. Lactose intolerance is a problem digesting milk sugar and is not dangerous. A milk allergy is an immune reaction to milk proteins and can cause anaphylaxis. Lactose-free milk is not safe for someone with a milk allergy.

Is coeliac disease an allergy?

No. It is an autoimmune disease triggered by gluten. It does not cause anaphylaxis, but small amounts of gluten still damage the gut, so strict avoidance is needed.

Can a food intolerance become an allergy?

They are different mechanisms, so one does not turn into the other. A person can have both, and new symptoms should be assessed by a doctor.

Should a restaurant treat an intolerance less seriously?

No. Staff cannot tell what a guest has, so every allergen request should be handled as if it were an allergy.

Food allergies and intolerances: what the difference is, and why it matters at the table

By the Menulta editorial team · Facts checked 15 October 2026 · Updated 15 October 2026

The short answer

A food allergy is a reaction of the immune system to a food protein. It can be triggered by a tiny amount and can cause anaphylaxis, which is life-threatening. A food intolerance does not involve the immune system in this way. It is usually a digestive problem, such as lactose intolerance, where symptoms depend on how much is eaten and are unpleasant but not life-threatening. Coeliac disease is a third category: an autoimmune reaction to gluten that damages the gut even when there are no obvious symptoms.

Food allergy: the immune system overreacts

In a food allergy, the immune system wrongly treats a protein in a food as a threat. In the most common type, IgE-mediated allergy, symptoms start within minutes to two hours: itching, hives, swelling of the lips or face, vomiting, wheezing, and in severe cases anaphylaxis, with breathing difficulty and a drop in blood pressure.

Very small amounts can be enough. A trace of peanut from a shared spoon or crumbs from a nut garnish can trigger a reaction. This is why cross-contact matters so much for allergic guests, and why 'just a little' is never acceptable.

There are also non-IgE food allergies, which are more common in babies and young children. Symptoms are slower and mostly affect the gut and skin.

Food intolerance: a problem digesting the food

Food intolerances do not involve this kind of immune reaction. The most common is lactose intolerance, where the body produces too little lactase, the enzyme that digests milk sugar. Others include reactions to FODMAPs, caffeine, histamine in aged or fermented foods, and some additives.

Symptoms are usually digestive: bloating, cramps, wind and diarrhoea. They are often dose-dependent, so many people with lactose intolerance can manage a splash of milk in coffee but not a creamy sauce. Intolerances can be very uncomfortable but are not life-threatening.

Coeliac disease: neither allergy nor intolerance

Coeliac disease is an autoimmune condition. Gluten, the protein in wheat, barley and rye, triggers the immune system to damage the lining of the small intestine. It is not an allergy and it does not cause anaphylaxis, but even small amounts of gluten cause damage, whether or not the person feels ill.

People with coeliac disease need strict avoidance, including cross-contact from shared toasters, fryers and flour-dusted surfaces. In EU law, 'gluten-free' on food means 20 mg/kg of gluten or less.

Side by side

Food allergy, food intolerance and coeliac disease compared
	Food allergy	Food intolerance	Coeliac disease
What reacts	Immune system (often IgE antibodies)	Digestive system	Immune system (autoimmune)
Typical trigger	Proteins in milk, egg, peanut, nuts, fish, shellfish and others	Lactose, FODMAPs, histamine, caffeine	Gluten in wheat, barley, rye
Amount needed	Can be tiny traces	Usually depends on the dose	Small amounts cause damage
Speed	Minutes to two hours (IgE type)	Hours, often	Hours to days; may be silent
Can be life-threatening	Yes (anaphylaxis)	No	Not acutely, but long-term harm
Restaurant approach	Strict avoidance and cross-contact control	Know the recipe; amounts matter	Strict avoidance and cross-contact control

Why restaurants should not try to tell the difference

Staff cannot know whether a guest has an allergy, an intolerance or coeliac disease, and guests use the words loosely. Treating 'I'm intolerant to dairy' as less serious is how mistakes happen, because some guests say 'intolerant' to avoid making a fuss about a real allergy.

The safe rule is to treat every allergen request as an allergy. Answer from the written record, check with the kitchen, prevent cross-contact, and say honestly when you cannot guarantee a dish is free from something.

Words guests use, and what to do with them

Guests describe their needs in many ways: allergic, intolerant, sensitive, coeliac, 'can't have', 'avoid'. Each of these should trigger the same response from staff: check the written record, confirm with the kitchen and handle the dish with care. Recording the exact words the guest used on the order ticket also helps the kitchen understand how strict to be with cross-contact.

Sources

This guide is general information, not medical or legal advice. Guests with an allergy should follow their doctor's advice. Operators should confirm their own setup with their food safety adviser or local authority.