Food Allergies and Intolerances

Knowing the difference, and getting reliable answers

Many people react to certain foods, but most reactions are an intolerance rather than a true allergy. The two are very different, and telling them apart matters for your health and for getting the right help. This guide is for information, not diagnosis.

The key difference

Food intolerance

Involves digestion, not the immune system
Milder symptoms: bloating, wind, cramps, diarrhoea
Can be delayed by hours or days
Small amounts are often tolerated

Food allergy

The immune system reacts to a food protein
Fast onset, minutes to a couple of hours
Even tiny traces can trigger it
Can be severe or life-threatening

Common intolerances

Lactose: not enough of the enzyme to digest the sugar in milk.
Non-coeliac gluten sensitivity: discomfort with gluten, distinct from coeliac disease.
Fructose malabsorption: trouble absorbing the sugar in some fruit and sweeteners.

The 14 allergens (UK law)

By law, UK food businesses must declare 14 allergens: celery, cereals containing gluten, crustaceans, eggs, fish, lupin, milk, molluscs, mustard, peanuts, sesame, soybeans, sulphur dioxide and sulphites, and tree nuts.

Reliable testing, and what to avoid

Trustworthy, through your GP: skin-prick tests, specific IgE blood tests, and supervised food challenges, plus careful food exclusion and reintroduction.
Not evidence-based: IgG blood tests, kinesiology and hair analysis. These are not recommended and can lead to cutting out foods for no reason.

Where to learn more: the NHS, Allergy UK, Coeliac UK, the British Dietetic Association (BDA), and the Food Standards Agency. For diagnosis of an allergy, coeliac disease or any medical condition, please see your GP.

This leaflet is general information and nutritional guidance for education only. It is not medical advice, diagnosis or treatment. Suspected allergies and medical conditions must be assessed by your GP or a registered dietitian. If you have a severe reaction, call 999.