Allergy testing

If you or your child are living with a suspected allergy, it may be important to have it tested. But testing isn't always straight forward, often requiring time, patience and commitment.

To help you understand the allergy testing process, we spoke to Paediatric Allergist/Clinical Immunologist Dr Shruti Swamy, who shares her top tips and insights.

Around one in 5 Australians experiences an allergic disease. And, unfortunately, numbers are on the rise, with an expected 70% of the population predicted to be living with allergies by 2050.¹

But what's caused this uptick?

"The reason is multifaceted," says Dr Swamy. "Apart from allergies generally running in families, there are multiple theories as to what goes into making the perfect allergic storm."

One reason may be the so-called 'clean theory', or 'hygiene hypothesis'. This theorises that reduced childhood exposure to infections (as a result of cleaner living standards) may explain rising allergy rates.²

Dr Swamy also points to epigenetics as another potential cause. "Kids who are born of parents who have come from Asian countries, for example, are more likely to have allergies," she says.³

Early use of antibiotics may be another potential contributor, as well as caesarean sections. While none of these in isolation result in allergies, the perfect combination in a susceptible individual can result in allergic disease.

Common allergies in Australia include:

• hay fever
• asthma
• eczema
• medication allergies
• food allergies (such as nuts, eggs or seafood).⁴

According to Dr Swamy, it's important to figure out whether a suspected allergy is, in fact, an allergy (or if it is, say, an intolerance).

"If a person has had an immediate onset allergic reaction, not an intolerance where they've had a tummy upset or diarrhoea, but a true 'IgE-mediated' allergy (immunoglobulin E), it would be important to get tested," she says. These allergies result in reactions soon after exposure to the offending agent (generally within 1 to 2 hours). At present, these types of allergies are the only ones that can be tested for in an evidence based manner.

While different allergies have different symptoms, some common reactions to look out for include:

• hives or urticaria (skin rashes)
• swollen lips, face or eyes
• a swollen tongue and tight throat
• sneezing or coughing
• wheezing
• watery eyes that are red and itchy
• a runny nose
• problems breathing
• headaches.⁴

"If you're worried that you or your child has something that's life-threatening, something that impacts your quality of life, and something which can result in unnecessary hospitalisations, it's important to get that looked into," says Dr Swamy.

According to Dr Swamy, there are 2 main tests that are considered useful in diagnosing an allergy. Both of these tests should be performed and interpreted by a health professional who has been trained in the field of Allergy.

This common allergy testing method involves exposing a person to a small amount of the suspected allergen through a prick in the skin, then waiting to see if they have an allergic reaction.

"It's a little scrape on the skin to see whether you have a reaction on the skin [break] to that allergen," says Dr Swamy. "This would be done to confirm the allergy if, for example, a child eats, say, peanuts, [and develops] hives, swelling or breathing difficulties."

"And then based on the size of [the skin prick test reaction], we can determine if the child has a risk of having an allergy to that allergen, keeping in mind that the size of the skin prick test doesn't predict severity." The results are generally available within 10 to 15 minutes.

The second common method to test for an allergy is a blood test, which may be used when skin prick testing isn't available, or for instance if you have severe eczema that prevents skin prick testing.

"This is a similar sort of test to skin prick testing, but in blood," says Dr Swamy. "You look at specific IgE antibodies made against allergens."

It is important to only test for the allergen that you suspect has given you or your child an allergic reaction.

Specialised tests are available, too, such as patch testing for allergic contact dermatitis.

However, Dr Swamy stresses the importance of avoiding certain tests which aren't standardised or evidence based. She recommends avoiding any allergy test with the word 'panel' in it, as well as several unproven tests such as food IgG (immunoglobulin G) testing and others outlined on the Australasian Society of Clinical Immunology and Allergy (ASCIA) website. These include cytotoxic food testing, kinesiology, hair analysis, vega testing (electro-diagnostic), Bryan's or Alcat tests, and IgG to foods.

"All that sort of stuff is completely unsupported and not based on any evidence, and can lead to dangerous food elimination and unnecessary costs," says Dr Swamy.

If the test is inconclusive, you or your child may be advised to ‘challenge' the suspected allergen.

"[This] is the gold standard in terms of a test for a food allergy," says Dr Swamy. "We feed [the patient] increasing amounts of that particular allergen to see if they're able to tolerate it. If they are, then they're cleared of the allergy. But if they're not, then they're diagnosed."

A positive diagnosis will usually result in one of 2 recommendations. Your doctor may advise you to avoid the allergen (in the case of a food allergy), or, if that's not possible, take medication to treat it (in the case of environmental allergies).

For those with severe allergy asthma and allergic rhinitis (hay fever), this may mean starting a course of immunotherapy, which involves gradually exposing someone to an allergen with the intention of desensitising them to it over time.

"Which is the closest thing we have to a cure," says Dr Swamy.

The Australasian Society of Clinical Immunology and Allergy (ASCIA) offers information and support for Australians and New Zealanders living with allergies, providing medical practice, training, education and research.

Allergy and Anaphylaxis Australia has online support resources available. You can also call for help and support on 1300 728 000.