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M&S Health & Nutrition

Allergies and Intolerances

Allergies and Intolerances

What is a food allergy or intolerance?

Food Allergies

Food allergy is an adverse immune response to a food, usually to the protein component and is distinct from other adverse reactions to foods such as food intolerances. Food allergies occur when the body’s immune system mistakenly thinks the protein component of a food is harmful. Allergic reactions are usually localised to a particular part of the body. Symptoms may include asthma, eczema, flushing, swelling of the tissues (usually the lips) or difficulty breathing.

The severity of the immune response varies in individuals. However, if someone has a severe food allergy they may suffer an anaphylactic shock (rapid fall in blood pressure and severe shock) which can be life-threatening.

Food allergies can be caused by any food but the most common foods are milk, eggs, wheat, peanuts, shellfish and fish.

Sometimes children grow out of their allergy during their childhood but others are present for life.

Food Intolerances

When a person is food intolerant, they will have a reaction to specific foods which does not necessarily result in an immune response. Though not generally life-threatening, intolerances can be extremely unpleasant and can result in a variety of symptoms such as constipation, diarrhoea, stomach bloating, headaches or skin rashes. These symptoms may not necessarily appear directly after eating the food and may take a few hours to develop.

If you think you may have a food allergy or intolerance, it is important to seek medical advice for proper diagnosis. A dietician will advise a diet plan to avoid the foods that are causing the allergy or intolerance. These websites are useful sources of further information: