Choosing Wisely Allergy tests

It’s not the only company offering pricey hair testing. Healthy Stuff Limited claims “hair is an excellent method of testing for intolerances”. For a “special” price of $90, it offers to test a sample of your hair to see if you’re intolerant to any of 300 foods plus 300 other potential allergens.

If you’re not keen on getting your locks looked at, there are plenty of other alternative tests – from iridology to IgG and kinesiology – promising to detect whether you may have an allergy to a food or anything else. But evidence any of these treatments work is lacking. There’s also a risk you’ll end up with an incorrect diagnosis.

Behind the claims

“In every clinic I run, throughout the course of the day at least one person will turn up who’s had hair testing or IgG testing and they’re usually quite surprised to learn there’s no scientific base to support their use,” immunologist Dr Andrew Baker says.

While there’s good evidence allergies are increasing, particularly food allergies, the number of incorrect diagnoses is also rising, he says. Companies touting hair and other alternative allergy tests can take part of the blame for that.

“These alternative tests almost universally come up with a very large number of so-called positive results and people are told to avoid a large number of different foods,” he says.

The upshot is people needlessly limit their diet, buy pricier products that provide no real benefit and unnecessarily worry about their health.

“There’s been a view among alternative practitioners that telling people to avoid lots of things isn’t going to do them any harm. But now we have evidence that diagnosing people as allergic to things when they’re not allergic can actually cause a lot of harm.”

The outcomes can be especially bad for children, Dr Baker says.

“A classic example is a 6-month-old diagnosed as allergic to nuts as a result of a hair test … Children are more likely to develop an allergy to peanuts if the food is excluded from their diet before age two. Evidence shows the introduction of solid foods to infants shouldn’t be delayed.”

Penny Jorgensen, adviser for Allergy New Zealand, knows of children put on restrictive diets due to an incorrect diagnosis of food allergies.

False negatives are another risk, she says. “Alternative tests may delay the correct diagnosis and management of a medical condition, whether allergy or something else, and could lead to a worsening of the underlying condition,” she says.

Allergy New Zealand and the New Zealand Clinical Immunology and Allergy Group have complained to the Commerce Commission about misleading claims made for alternative tests. In 2012, the commission put companies on notice to review their claims to ensure they complied with the Fair Trading Act.

Dr Baker says claims decreased following the commission’s warning but the lull didn’t last.

Getting a diagnosis

If you’re worried you have an allergy and want to get tested, see your GP, Ms Jorgensen advises.

Allergies affect an estimated 30% of people. Allergic reactions happen when your immune system overreacts to something you come into contact with. Common offenders include dust mites, grass, pollen, metals and animals, as well as food.

“Diagnosis of allergies is based primarily on the patient’s clinical history … Most allergic reactions happen within minutes, rarely beyond 2 hours of exposure to the trigger, and will resolve once the patient is no longer exposed. So in many cases, if it is an ‘allergy’, it may be obvious what the trigger is,” she says.

Skin prick or blood tests are usually done to help diagnose the cause. These tests are used to detect immunoglobulin E (IgE), an antibody produced in response to the presence of an allergen.

With a skin prick test, the skin on your forearm or back is pricked with a needle that contains a tiny amount of the potential allergen and the reaction measured (a weal on your skin indicates whether you may be allergic to the substance).

A blood test may be recommended if skin testing isn’t considered suitable – for example, you take a medicine that could affect the results.

A positive result doesn’t necessarily mean you’re allergic to the substance. The most important thing is whether the results match the person’s symptoms, Dr Baker says.

“Interpretation of tests can only be done in combination with a history of a patient’s symptoms to see if these are consistent with the allergy.”

There’s no cure for allergies but allergen immunotherapy – or desensitisation – may be recommended for the treatment of hay fever caused by pollen or dust mites when symptoms are severe and medications don’t help or cause adverse side effects. The treatment involves gradual doses of the allergen over several years.

If you’re diagnosed with a food allergy, your only option is avoiding the food. Research into immunotherapy for food allergies is ongoing and it’s not yet recommended.