Australia has one of the highest allergy rates in the world, and the number of people affected is growing at an astonishing rate. It's now estimated that 1 in 20 children have a food allergy (some estimates are as high as 1 in 10 children) and 1 in 100 adults.

According to experts, the explosion is a relatively new phenomenon. "The allergy wave hit in the 1990s. 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.

Deadly nut allergies

It's not every type of food allergy that's skyrocketing. Data from child care centres in the ACT and Central Sydney Area Health Service shows that 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 by a staggering five times.

Nut allergies tend to evoke a much more severe reaction than many other kinds of allergies do, raising concerns about exposure to nuts for high-risk young children.

Why are nut allergies increasing now?

There are a number of theories, all as yet unproven, which might explain the increase in nut allergies in recent years, but one theory is that 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 Children's Hospital Westmead, Sydney, one explanation suggests a relationship between allergies and exposure to bacteria through soil and animals; for example, people living on farms are less affected by allergies 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 age that we introduce solids to babies, changes in food processing and mothers' diets 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. So at first it was peanuts and cashews, with cashews now having overtaken peanut allergies, and walnut allergies are on the increase.

What's the cause for kids?

You can't be allergic to something your body's never been exposed to – there has to be a first exposure that sensitises a susceptible person, so that the next time they're confronted with that foreign protein their immune defence goes into overdrive. Experts say there's an early window for sensitisation, generally agreed to be 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 scratchy 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.

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).

What is Coeliac disease?

Coeliac disease is an autoimmune disease that causes the immune system to react 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 coeliac.org.au for more information.

Intolerance or allergy?

It is the number of people with food allergies, not intolerances, that's on the rise according to experts. The difference between the two is often confused; many people think they're allergic to something when really they're just intolerant of particular food chemicals. The table below explains the difference, and how to work out which you might have.

Food allergy or intolerance
  Allergy Intolerance  
Symptoms Eczema as a baby (especially on the face). Acute reactions: rash around mouth; hives / swelling; vomiting; difficulty breathing; anaphylaxis. In adults: occasional, recurring or chronic hives / swelling; stomach / bowel irritation; headaches / migraines; fatigue / aches / pains; mouth ulcers; sinus congestion / polyps.
In children: irritable behaviour (coloc, screaming, disturbed sleep, leg aches / pains, ADHD); reflux (from birth); eczema / itchy rashes; nappy rash.
 
Age when first noticed Mostly infants and toddlers. At any age - children or adults.  
Speed of reaction Immediate (from minutes to 1-2 hours). It happens every time you eat the food. Can happen hours or days after eating the food. It may only happen sometimes.  
Most likely food triggers Specific food proteins: egg, milk, peanut, other nuts, sesame, fish, crustaceans. Natural chemicals in foods: salicylates, amines, MSG. Additives in food.  
How to test Through your GP or an allergy clinic or specialist. Through your GP or an allergy specialist or specialist dietition or allergy clinic.  
What can you do? Completely avoid the food(s) you are allergic to. Comprehensive diet overhaul to keep chemical intake below your reaction level.  
Most likely outcomes Egg and milk allergy is usually outgrown. Most nut and seafood allergies (70%-80%) are lifelong. Intolerances are usually lifelong, although symptoms and tolerance levels can come and go.  
Source: RPAH Allergy Unit

According to Dr Anne Swain, Chief Allergy Dietitian at RPAH, many people have a food intolerance, but haven't yet 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.

Introducing allergenic foods to babies

At the end of 2008, the Australasian Society of Clinical Immunology and Allergy (ASCIA), the 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 at 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.

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 the introduction of allergenic foods could contribute to higher allergy rates. Some studies are underway 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 high-risk families introduce new food to babies cautiously; try a little on their lips or face first, for example. For more information on allergies, go to allergy.org.au where you can follow links to a list of allergy and immunology specialists in Australia and New Zealand.

Allergy tests

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 an incorrect 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

While testing is available for food allergies and intolerances, be wary of tests not conducted by a GP, allergy specialist or paediatrician – some appear no more reliable than reading tea leaves.

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 either. There's no scientific evidence to support any of the following 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 diluted 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 by 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 by 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 by changes in an individual's electromagnetic field, which is 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

This 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)