Is food making you ill?

24 September 2012

Go out to a restaurant with friends, or take your child to a birthday tea and chances are there will be someone there who cannot eat something because they have a food allergy.

But true allergic reactions to food are actually far less common than most of us imagine, according to Professor Barry Kay, Consultant Allergist at the London Clinic. 'Food allergy, which happens when someone eats a particular food and their immune system produces what we call IgE antibodies, causing a particular set of symptoms [see 'Symptom Watch'] immediately or shortly after eating the offending food, is clear-cut, uncontroversial and can be confirmed scientifically by an allergy test,' he says.

'It can also be extremely serious.' In fact, if you have a severe food allergy, eating even a minute amount of the wrong food causes a reaction called anaphylaxis: breathing difficulties, swelling of the lips and throat, abdominal pain, vomiting, collapse and, in the worst-case scenario, it can lead to death.

Allergy or intolerance?

Experts still don't know how many of us are affected by food allergy, but it appears to be on the rise. 'The trouble is that many people who believe they have a food allergy are actually experiencing food intolerance, or non-allergic food hypersensitivity,' says dietitian Helen Bond, a spokesperson for the British Dietetic Society.

'In fact, although around 30 per cent of people claim to be allergic to one or more foods, only 1 to 2 per cent of adults have a true food allergy and 5 to 8 per cent of children. But, food intolerance is far more common and may affect as many as 45 per cent of people according to some estimates,' she adds. While food allergies normally occur in reaction to a fairly limited number of foods, (see '10 Common Culprits') food intolerance reactions are more idiosyncratic and occur when you eat foods that most people can tolerate without a problem making them quite hard to diagnose.

As Dr Anton Emmanuel, Consultant Gastroenterologist, senior lecturer in Neuro-gastroenterology at University College, London, and expert adviser to Food Intolerance Awareness, part of AllergyUK, explains: 'The main problem is that food intolerance is unpredictable: sometimes a reaction happens and sometimes it doesn't, while symptoms are wide-ranging and can be vague, although often they affect the digestive system.'

Symptoms of food intolerance can be caused by lack of the enzymes needed to digest certain foods, e.g. lactase, an enzyme needed to digest the milk sugar lactose, causing lactose intolerance. They can also be caused by an abnormal sensitivity to certain ingredients in foods, additives and preservatives, such as tyramine, found in mature cheeses and yeast extract as well as certain wines that causes migraine. Alternatively they may be toxic reactions to food (e.g. food poisoning).

Meanwhile, coeliac disease, which is not an allergy or an intolerance at all but a unique and complex immune reaction, can trigger symptoms (see 'Symptom Watch') when an affected person eats gluten, which is a protein found in bread, pasta, biscuits, and a host of other foods containing wheat, barley, rye and, to a certain extent, oats. This damages the surface of the gut, thereby making it hard to absorb certain nutrients.

10 Common culprits

You can get an allergic reaction to any food, but these are the top offenders...

  • Peanuts and products containing peanuts
  • Soya and soya products
  • Egg and egg products
  • Milk and milk products
  • Fish and fish products
  • Wheat and products containing wheat
  • Shellfish (e.g. shrimps, prawns, lobster, crab, crayfish, clams, mussels, oysters and scallops)
  • Fruit - apples, pears, kiwi fruit and peaches are common culprits in adults
  • Vegetables - potatoes, carrots, celery and parsnip in adults
  • Tree nuts and products containing tree nuts - almonds,Brazils, hazelnuts, cashews, macadamia, pecan, pine nuts, pistachios, and walnuts

Are you at risk?

Babies and children under three are most at risk of food allergy and intolerance, because their digestive and immune systems are immature. The good news is that most grow out of food allergies by the time they reach school age. However, an estimated four out of five children with a peanut allergy, one of the foods most likely to trigger severe allergic reactions, will stay allergic for the rest of their life.

Allergies can persist into or emerge for the first time in adulthood. Doctors still don't know the reason, although people with a family or personal history of asthma, eczema, hayfever and other allergies are more at risk.

Testing, testing

It can be hard to get a diagnosis of food allergy or intolerance. For a start, as Helen Bond observes, 'We eat diets rather than single foods and the delay that can occur between eating a suspect food and the reaction can make it hard to catch the culprit.' 'What's more,' she adds, 'because it is quite common to be intolerant to several different foods at the same time it can be hard to determine exactly which foods are responsible.'

It can be helpful if you keep a food diary and note down everything you eat - or your child eats - any symptoms that occur and when they happen, to see if you can pinpoint any patterns. If food allergy is suspected, your doctor can also refer you to an allergy expert for further tests. These include skin prick tests, in which a minute amount of suspect food is placed on your skin which is pricked to see whether it creates a wheal; blood tests, which measure the amounts of IgE antibodies in your blood; and also oral food challenges in which you are given a small amount of a suspect food to eat concealed in another food to avoid psychological reactions, and watched for any symptoms. This must be done under medical supervision just in case an offending food causes a severe reaction. If you have a food allergy or intolerance, you may also be asked to follow an elimination and challenge diet. This is when you leave out any suspect foods for a certain period before reintroducing small amounts of them into your diet one at a time, to help establish which specific foods cause symptoms. Never undertake an elimination and challenge diet without medical supervision if you or your child have severe asthma, eczema or have ever had a severe allergic or anaphylactic reaction to food. Food allergies that occur during adulthood are usually there for good.

However, in the case of food intolerances you may find that, after a period of avoidance, you are able to tolerate small amounts of the offending foods. It's a question of trial and error to see how much you can consume before you get symptoms. If you - or your child - are leaving foods out of your diet on a regular basis, then it's vital to get advice from a health professional, such as a doctor or a dietitian, to make sure that you are getting all the nutrients you need from other sources.

Be a food detective!

If you're hypersensitive to food then you need to read labels. All pre-packed foods and drinks must, by law, be clearly labelled if they contain the following 14 ingredients:

  • Celery
  • Cereals containing gluten (e.g. wheat, rye, barley and oats)
  • Crustaceans (shellfish, including prawns, crabs and lobsters)
  • Eggs
  • Fish
  • Lupin (a common garden plant, seeds from some varieties are sometimes used to make flour)
  • Milk
  • Molluscs (soft-bodied shellfish including mussels and oysters)
  • Mustard
  • Tree nuts (almonds, pecans, hazelnuts, walnuts, pistachios, cashews, macadamias,Brazils)
  • Peanuts
  • Sesame seeds
  • Soybeans
  • Sulphur dioxide and sulphites (SO2) used to preserve some foods and drinks at levels above 10mg/kg, or 10mg/litre

Some food manufacturers will also use phrases such as 'may contain' nuts, eggs, milk, soya, etc, to show that there could be small amounts of these foods present either in the ingredients, or because the food may have been contaminated accidentally during manufacture.

Eating out

Unpackaged foods from restaurants, delis, take-away food outlets and bakeries can be trickier, as they do not have to be labelled. When eating out warn the staff that you or your child has an allergy and make sure both the chefs and the waiters know so they can avoid cross-contamination of your meal with other diners' food. Be aware of hidden allergens, e.g. in desserts, which may contain nuts (e.g. in a cheesecake base), and sauces, which contain wheat and peanuts.

Symptom watch

If you experience any of the following symptoms...

Nervousness, tremor
Rapid breathing
Headache, migraine
Diarrhoea and/or constipation
Burning sensations - skin
Tightness across face and chest
Breathing problems
Tiredness and lethargy
Aches and pains
Stomach cramps
Skin problems
Restless legs

 ...hours or days after eating a could have a food intolerance

Tingling or burning lips/mouth
Swelling of lips, face, throat
Itchy, blotchy rash
Hoarseness (caused by
swelling of the voice box)
Dizziness and lightheadedness
Cold-like symptoms
Breathing difficulties/wheezing
Nausea and/or vomiting
Red, irritated eyes
Abdominal pain
Chest tightness

...immediately or shortly after eating a particular could have a food allergy

Abdominal cramps
Recurrent mouth sores
Skin rashes

...after eating wheat, rye or could have celiac disease

Where can I get further information?

Apart from contacting your GP, the following organisations may be of further help:

Allergy UK
Deepdene House
30 Bellgrove Road
DA16 3PY
Telephone: 01322 619898

Food and Chemical Allergy Association
27 Ferringham Lane
West Sussex
BN12 5NB

Booklet 'Understanding Allergies' sent for £2.00 and a medium SAE.

National Society for Research into Allergy (UK & International)
PO Box 45
LE10 1JY
Telephone: 01455 250715

Raising awareness of allergy and intolerance. Membership is £15 per year.