What’s the difference between a food allergy and intolerance, how do you know if you have one or the other, and what are the best ways to manage it?
Confusion around food allergies and intolerances is not unusual, with many of us growing wary of certain foods we believe might be the cause of unwanted symptoms – leaving them out of our diets ‘just in case’. But should we – are true allergic reactions to food far less common than most of us imagine?
“A food allergy is when someone eats a particular food and their immune system reacts by producing ‘IgE antibodies’, which travel to cells that release chemicals, causing an allergic reaction [see 'Symptom Watch']. It can easily be confirmed scientifically by an allergy test,” says Ceitanna Cooper, registered associate nutritionist (ANutr) at AXA Health.
Symptoms of food allergies vary. For anyone with a severe allergy, eating even a minute amount of the ‘wrong’ food can cause a reaction called anaphylaxis, resulting in breathing difficulties, swelling of the lips and throat, abdominal pain, vomiting, collapse and, in the worst-case scenario, it can tragically lead to death.
But this is rare. In fact, research using conventional testing procedures, suggests that between 1 and 2 in 100 Brits (1-2%) have a food allergy that can be diagnosed reproducibly, whereas as many as 30 in 100 (20-30%) ‘believe’ themselves to be allergic or intolerant to one or more foods.*
“Many people believe they have a food allergy, but are actually experiencing food intolerance, which is when a person has difficulty digesting food, resulting in abdominal pain, intestinal gas or diarrhoea, although unpleasant and worrying, it doesn’t affect the immune system,” says Ceitanna.
While food allergies normally occur in reaction to a fairly limited number of foods, (see '10 Common Culprits') food intolerance reactions are unpredictable – sometimes they happen, sometimes they don’t and the symptoms can vary each time you eat, making diagnosis difficult.
Ceitanna says: “Symptoms of food intolerance can be caused by lack of the enzymes needed to digest certain foods, for example, 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, like additives and preservatives, such as tyramine, found in mature cheeses and yeast extract, as well as certain wines that may cause migraines.”
Meanwhile, coeliac disease, which is neither an allergy nor an intolerance at all but a unique and complex immune reaction, can trigger symptoms (see 'Symptom Watch') when an affected person eats gluten - a a protein found in bread, pasta, biscuits, and 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.
“Some people can confuse intolerance or sensitivity to wheat products with coeliac disease and choose to leave gluten out of their diets completely, which isn’t recommended without testing. Gluten contains fibre, iron and folate, which are really beneficial nutrients, so a decision to leave it out shouldn’t be made lightly.”
10 common culprits
You can get an allergic reaction to any food, but these are the most common:
- 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 history of asthma, eczema, hayfever and other allergies are more at risk.
“It can be hard to get a diagnosis of a food allergy or intolerance. We could be allergic or intolerant to several foods at the same time, making it hard to determine exactly which foods are responsible, and the delay that can occur between eating a suspect food and the reaction can make it hard to know the cause”, says Ceitanna.
It can be helpful to keep a food diary, writing 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 your doctor suspects you have an allergy, they can refer you to an allergy expert for further tests, which could 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 (burning, itching or swelling)
- Blood tests, which measure the amounts of IgE antibodies in your blood
- Oral food challenges – in which you are given a small amount of a suspect food to eat 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 elimination 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.
“If you’re going to eliminate certain foods, it’s best to pick one food at a time so that you don’t become deficient in too many nutrients at once”, says Ceitanna.
However, in the case of food intolerances you may find that, after a period of avoidance, you’re able to tolerate small amounts of the offending foods. It's a question of trial and error to see how much you can eat before you get symptoms. If you - or your child - are leaving foods out of your diet on a regular basis, then it's important to get advice from a health professional to make sure that you are getting all the nutrients you need from other sources.
Know what you’re eating
All pre-packed foods and drinks must, by law, be clearly labelled if they contain the following 14 ingredients:
- Cereals containing gluten (e.g. wheat, rye, barley and oats)
- Crustaceans (shellfish, including prawns, crabs and lobsters)
- Lupin (a common garden plant, seeds from some varieties are sometimes used to make flour)
- Molluscs (soft-bodied shellfish including mussels and oysters)
- Tree nuts (almonds, pecans, hazelnuts, walnuts, pistachios, cashews, macadamias,Brazils)
- Sesame seeds
- 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.
If you experience any of the following symptoms...
- 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 food...you could have a food intolerance.
If you experience any of these symptoms…
- Tingling or burning lips/mouth
- Swelling of lips, face, throat
- Itchy, blotchy rash
- Hoarseness (caused by swelling of the voice box)
- Dizziness and light-headedness
- Cold-like symptoms
- Breathing difficulties/wheezing
- Nausea and/or vomiting
- Red, irritated eyes
- Abdominal pain
- Chest tightness
...immediately or shortly after eating a particular food...you could have a food allergy.
If you experience any of the following:
- Abdominal cramps
- Recurrent mouth sores
- Skin rashes
...after eating wheat, rye or oats...you could have celiac disease.
If you experience any unusual or worrying symptoms after eating food, it’s best to check with your GP, who can advise you on the next steps to take.
Sources and further reading
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Diet and nutrition centre – AXA Health