Food allergies and intolerances

CHOICE investigates why nut allergy rates are now soaring, and what you can do if you think you have an allergy.
 
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01 .Introduction

Food allergies and intolerances

In brief

Nut allergies are growing at a faster rate than any other kind of food allergy, raising concerns about exposure to nuts for high-risk young children.
Testing is available for food allergy and intolerance, but be wary of those not conducted by a GP, allergy specialist or paediatrician – some appear no more reliable than reading tea leaves.

Australia has one of the highest allergy rates in the world, and the number of people affected is growing at an astonishing rate. The number of children aged under five ending up in hospital with a life-threatening allergic reaction (anaphylaxis) increased fivefold in the decade to 2007.

According to experts, the explosion is a relatively new phenomenon. “The allergy wave hit 10 to 15 years ago. It’s an epidemic … and it’s growing exponentially – we’re swamped,” says Dr Rob Loblay, head of Royal Prince Alfred Hospital’s (RPAH) allergy clinic in Sydney.

But it’s not every type of food allergy that’s skyrocketing. Data from childcare centres in the ACT and Central Sydney Area Health Service shows while allergies to proteins in milk, eggs and seafood have remained steady, peanut allergies increased by 50% between 2003 and 2006, and cashew allergies, while less common overall, increased a staggering five times.

Please note: this information was current as of March 2009 but is still a useful guide today.


Why are nut intolerances increasing now?

There are a number of theories, all as yet unproven, which might explain the increase. It could be related to Western lifestyles – as countries become more developed and prosperous, allergy rates increase.

According to Dr Andrew Kemp, Professor of Paediatric Allergy at Childrens’ Hospital Westmead, Sydney, one explanation suggests a relationship between allergies and exposure to bacteria through soil and animals; people living on farms are less affected than those in cities and towns. And experts such as microbiologist and immunologist Dr Mary Ruebush, author of the book Why Dirt is Good, argue that our modern dirt phobia means children’s immune systems don’t get the opportunity to develop properly, and this could play a part in this very modern problem.

Other possible explanations include the timing of introduction of solids to babies, changes in food processing and the mother’s diet during pregnancy. Dr Anne Swain, Chief Allergy Dietitian at RPAH, also points to the changing consumption patterns of nuts. As the popularity, availability and affordability of a type of nut grows, she says, so do the allergy cases. “It’s peanuts and cashews now, but walnuts and macadamias look like the next wave.”

Why do kids become allergic?

You can’t be allergic to something your body has never seen – there has to be a first exposure that sensitises a susceptible person, so that the next time he or she is confronted with that foreign protein their immune defence goes into overdrive. Experts say there’s an early window for sensitisation, around two to four months of age.

So exposure to nut proteins via breast milk is one possibility. But there are other theories on the possible ways babies could be exposed, such as through smooches from dads after they’ve eaten nuts (broken skin from beard rash can allow the foreign proteins in), or through broken skin from eczema letting allergens in if there are nuts around. Nappy rash cream, which sometimes contains peanut oil, could also be a culprit, particularly as it’s often used on broken skin.

More research is needed to find out what’s really behind the trend, and a number of studies are under way. Loblay and Swain, for example, are investigating whether the risk could be reduced by minimising the likelihood of contact between baby and nut allergens during pregnancy, breastfeeding and in the first months of life. They say that while studies show changing the mother’s diet during pregnancy and breastfeeding doesn’t reduce the risk of allergy, they don’t take into account other contact with nuts.

Allergies in adulthood?

Allergies are usually discovered in childhood. Most problems in later life are likely to be intolerances. However, it is possible for adults to discover an allergy to something they’ve only recently come into contact with, such as insect stings, drugs or dust/pollen (after moving to a new environment).

 
 

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Intolerance or allergy?

It is the number of people with a food allergy, not intolerance, that is on the increase, according to experts. The difference between the two is often confused; many people think they are allergic when they are really intolerant to particular food chemicals. The table below explains the difference and how to work out which you might have

According to Dr Anne Swain, Chief Allergy Dietitian at RPAH, many people have an intolerance, but haven’t identified it as such; they just know they associate their migraines with chocolate, or feel awful after eating particular foods. It’s not easy to measure how widespread this is, but as a rough estimate 10% to 15% of people may have some form of intolerance, with only a few experiencing serious problems.

Table

What is Coeliac disease?

Coeliac diseaseis an autoimmune disease where the body’s immune system reacts abnormally to the protein gluten, and attacks and damages the lining of the bowel. It spells a lifetime of avoiding gluten, which is found in wheat, rye, oats and barley. People with coeliac disease have a genetic predisposition to it, but as environmental factors play a part it can develop at any time. Blood tests can point to the disease, but diagnosis can only be confirmed by taking a biopsy of the small bowel and checking for damage. Visit www.coeliacsociety.com.au for more information.

What to feed baby

At the end of 2008, the Australasian Society of Clinical Immunology and Allergy (ASCIA), peak body of Australian and New Zealand clinical immunologists and consultant allergy physicians, reviewed traditional advice for delaying the introduction of certain foods for babies. Previously, the advice for milk and eggs was to delay their introduction until about eight months, and nuts until two years old.

After reviewing the published evidence, ASCIA concluded there was no evidence that delaying allergenic foods, such as eggs or milk, actually prevented allergies. The new ASCIA advice on infant feeding includes introducing foods the family eats (ensuring the texture is appropriate), starting by around six months old, when your baby is ready – ideally when breastfeeding. It advises starting with plain cereals, then adding a new family food every few days.

Introducing allergenic foods to babies

ASCIA says there aren’t any particular allergenic foods that need to be avoided, although you should take care with the texture of foods to minimise the possibility of choking. ASCIA’s evidence also suggests it’s possible, though not proven, that delaying introducing allergenic foods could contribute to higher allergy rates. Some studies are under way to find out whether earlier introduction of allergenic foods might actually help reduce the incidence of allergies in children.

The ASCIA advice is relevant to all babies, whether or not there’s a family history of allergy or reason to think the baby might be at high risk. Some experts, however, suggest their high-risk families introduce new food cautiously; try a little on their lips or face first, for example. For more information on allergies, go to the ASCIA website where you can follow links to a list of allergy and immunology specialists in Australia and New Zealand.

True allergies are tested by measuring particular immune factors in the body, called Immunoglobulin (IgE) antibodies, which are measured using skin prick tests or RAST blood tests. But how these tests are interpreted is important, as some people can have low levels of food-specific IgE without any allergy problems. Seeking the advice of an immunologist or allergy specialist is sensible – a lifetime of avoiding foods unnecessarily is a hassle and can mean you miss out on some essential nutrients.

Food intolerance, on the other hand, can’t be measured by any blood or skin test . The road to working out which foods (and how much of them) might trigger your symptoms is a long haul following a low-chemical elimination diet and, if your symptoms improve over several weeks, challenging your body with individual foods or food chemicals at increasing doses. It’s a trial-and-error process that can take months. Sadly there are no quick fix tests, but a wrong diagnosis can mean you spend years on complicated and costly special diets you don’t need. Seek the advice of your GP and get a referral to a specialist clinic or dietitian for help and advice.

Alternative allergy tests not recommended

The Australasian Society of Clinical Immunology and Allergy (ASCIA) has reviewed a wide range of other tests for allergies and didn’t find any worth wasting your time or money on – and there’s no Medicare rebate for any of them. There is no scientific evidence to support any of these allergy ‘tests’ :  

  • Cytotoxic testing Some of your white blood cells are mixed with dried foods and studied under a microscope. A change in the cells is said to represent a sensitivity or allergy.
  • Oral provocation and neutralisation Drops of dilute allergen extracts are placed under your tongue and the amount needed for a reaction is assessed. Before you eat an offending food you use drops of a more dilute solution to stop symptoms.
  • VEGA (electrodermal) testing This is based on the idea that illness is reflected in a change in the body’s electrical charge which can be measured by a VEGA machine. You hold one electrode and another is placed on acupuncture points on your fingers or toes. A food extract in a sealed container is put into the loop – a reduced electrical current means a sensitivity. Children are tested by holding the parent’s hand during the test.
  • Kinesiology Exposure to toxins or allergens is claimed to be reflected in reduced muscle strength, which is measured before and after drops of suspect food extracts are put under your tongue or held in your hand. Children are tested by holding the parent’s hand while the test is done.
  • Radionics (psionic medicine, dowsing) Disease is claimed to be reflected in changes in an individual’s electromagnetic field, which are said to lie outside the normal electromagnetic spectrum. Practitioners say they can detect subtle changes in the energies and vibrations of internal organs by using a pendulum-like device to amplify the changes. By focusing their thoughts and energies, the practitioner claims to treat the problem by restoring energy balance. In some cases the test can be done at a distance, using a lock of the patient’s hair, for example.
  • Iridology Iridologists believe each part of the body is represented by a part of the iris and your health is reflected in the appearance of the appropriate part. Imbalances are treated with dietary supplements or herbal medicines.
  • Pulse testing Proponents claim allergic reactions change nerve impulses and can be measured by an increase in heart rate.
  • Hair analysis A sample of your hair is measured for trace elements and deficiencies or excesses related to your symptoms.
  • Dysbiosis This is the theory that imbalances of good and bad bacteria in the bowel result in diseases. Various metabolic and bacteriological measurements (stool analysis, blood and urine tests, etc) are done to assess the balance. Imbalance is usually treated with large doses of vitamins/minerals, probiotic or antibiotic therapy, or diet changes.
  • VoiceBio is based on the concept that your internal organs communicate with each other by sound, each organ vibrating at a certain frequency. It’s claimed unhealthy organs can be detected by using computer-assisted analysis of your voice.

Source: Australasian Society of Clinical Immunology and Allergy (ASCIA)

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