Food allergy or intolerance?

How many times have you heard people say that they're on a wheat - or dairy -free diet? Or that they can't eat anything containing nuts? Excluding certain foods from your diet is so common now that most people have probably forgotten why they started doing it in the first place. The main reasons are a food allergy or intolerance. But, what is the difference?

A food allergy is a reaction by the immune system that happens quickly, dramatically and can be life threatening. Allergies are usually connected to peanuts, but they can also be brought on by eggs, milk and almost any other food,' explains Linda Gamlin, author of 'The Allergy Bible' (£12.99, Quadrille).

'A food intolerance is more gradual – and never life threatening. The symptoms are much more varied and can include anything from headaches and migraines to bowel problems and even quite general problems such as fatigue. They can also be associated with psychological problems, depression or anxiety, say.'

If you have a food allergy, you will know about it. An allergic reaction to peanuts or shellfish, for instance, produces local symptoms such as swelling in the lips, tongue and mouth within a couple of hours and, in more extreme cases, may induce anaphylaxis and collapse from anaphylactic shock. Around two per cent of the population have true allergies, usually to foods that are not eaten everyday.

According to Allergy UK, around 40-45 per cent of people in the UK suffer from a food intolerance. However, it is more difficult to detect; reactions may not occur until 72 hours after consuming the food to which you are sensitive. Intolerances are associated with food that we eat on a regular basis, such as alcohol, wheat, gluten and cow's milk.

Symptoms can be tricky to pin point – constipation, gas, heartburn, cravings, muscle pains, water retention and weight gain to name but a few – and are often associated with conditions such as asthma and irritable bowel syndrome (IBS). In children, a sign of a food intolerance might be a stomach ache, skin disorder or behavioural problem.

So, how can you tell if you or someone in your family is affected? While there are numerous tests on the market that claim to help identify where the problem lies, Gamlin says there is only one accurate and dependable method: an elimination diet.

She recommends you start by keeping a detailed food diary of everything you eat for two weeks and noting down how you feel. Before progressing further, consult your doctor, especially where children are concerned. If you suffer from Chrohn's disease or eczema there may be complications.

The next stage involves excluding the foods you normally eat, as well those in the same food group. If you think cow's milk is the culprit, then cut out cheese, yoghurt and all other dairy products.

Although you may feel worse before you feel better, symptoms clear up within seven to eight days. Over the next eight weeks, you can then experiment by carefully reintroducing foods one by one until you have a clear picture of what is causing the reaction.

When following an elimination diet ensure that you are getting all the nutrients you need – protein and calcium, for example – from other sources. Sufficient starchy foods that will provide you with energy and keep hunger at bay are important, too.

An elimination diet takes willpower at first. But the benefits can be considerable. 'If you have a food intolerance - and have had it for a while - you will probably be feeling awful,' says Gamlin. 'All sorts of apparently unconnected problems, such as getting the shakes if you don't eat regularly, may suddenly clear up. You will have forgotten what it's like to feel so well; it's a revelatory experience.'

The good news is that, unlike a food allergy, a food intolerance doesn't mean you have to go without forever. Enjoy a slice of bread or cheese now and again, just not more than every few days or once a week. In the meantime, there are plenty of other tasty alternatives that will keep you satisfied and bring exciting variety to your diet.

Allergy UK can put you in touch with a local allergy specialist and provides free fact sheets on food allergies and intolerances. Visit www.allergyuk.org or call 01322 619898.