According to the charity Allergy UK (allergyuk.org) a “true” food allergy is very rare, affecting only 1 to 2 per cent of the population. It occurs when the body mistakenly makes an antibody to “fight off” an offending food. When that food is eaten, it triggers an immune response that results in the release of histamine and other chemicals in the body. Symptoms range from abdominal pain, vomiting and diarrhoea to sneezing and coughing and usually become apparent within a couple of minutes of eating the food.

Common food allergies: Milk, eggs, nuts, seeds, shellfish, fish, wheat (coeliac disease), soya, citrus and fruit.

What to do: Ask your GP to refer you for tests. Reliable and accurate blood and skin-prick tests are available on the NHS.

Food intolerance: A food intolerance is much more common than food allergies. However, they are difficult to diagnose and define. The onset of symptoms with an intolerance is often slower and can happen hours after an offending food is eaten. Symptoms are also more variable and include IBS, joint pain, rashes, eczema and migraine headaches.

What to do: Because there are so many different reasons why someone might develop a food intolerance (from the chemicals and additives in food to the food itself), there is no easy way to diagnose it. No reliable blood or skin tests are available apart from the well-researched intolerances to gluten and lactose and, according to Allergy UK, there are no cures for a food intolerance. The most accurate way to diagnose and treat the problem is through an elimination diet in which foods are removed from the diet to see if symptoms disappear. These should only be carried out on consultation with a state-registered dietician on referral from your local doctor.

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