Are allergy tests actually helpful?

Experts weigh in on the accuracy of allergy tests and navigating their often-confusing results

Groundnut, lemon, sesame, tomato, clove–foods that are usually found on a grocery shopping list, are actually the many items that showed up in the results of an allergy blood test I took a few years ago. What I hoped would offer clarity, left me feeling confused. I didn’t know how to go about eliminating so many different things that were also key ingredients in my favourite meals (is a pizza without a rich tomato base really pizza?), and I found myself wondering if there really was a need to stop eating foods that hadn’t resulted in any reactions in the past. Over the years, conversations with family and friends on this subject gave rise to similar questions. Are the often-expensive tests really worth taking? Is one method of testing more accurate than the other? How do you approach the results without embracing extremes? Armed with these questions, and more, we reached out to various experts and here’s what they had to say.

Allergies versus intolerances

The first step is identifying whether what you have at hand is an allergy or an intolerance. For a while, I experienced uneasiness after drinking a cup of hot chocolate or eating anything particularly milky. So I decided to dig deeper with a test. I was certain that dairy would crop up in the results but it didn’t. What I learnt much later than I should have was that I was trying to detect an intolerance with an allergy test. “An intolerance is a gut response and an allergy is an immune reaction. While there can be an overlap between intolerances and allergies, an intolerance can’t be diagnosed through an allergy test. It’s more of a clinical diagnosis with certain other blood tests or invasive tests. For example, an intestinal biopsy can diagnose coeliac disease, also known as gluten intolerance,” says pediatrician Nergis Damania.

Allergies and intolerances, adds integrative nutritionist Payal Kothari, are often erroneously used interchangeably. “People tend to confuse both these terms. With food intolerances, you may be able to consume the food in smaller amounts; allergies cause an instant reaction,” she says. In addition to the speed, explains Damania, the intensity of the reaction is also increased when it comes to allergies. “The signs and symptoms of an allergy manifest much faster and you can see, including reactions ranging from rashes to breathlessness within minutes to a few hours. If you’re intolerant to gluten you may not see a reaction if you have a small piece of toast but consuming it for a few consecutive days will lead to the manifestation of symptoms,” she says.

The options and their accuracy

When you suspect that your symptoms go beyond mild discomfort and are more immediate reactions, you should investigate further with an allergy test. The next, and often overwhelming step, is to then zero in on a test that gives you the most accurate results. For the average person, the options aren’t always easy to choose from and can lead to the investing of time, energy and money in something that ultimately throws you off track. When asked which out of the many methods available are recommended, allergists, both in India and internationally, said they favour skin tests for a few reasons. “The best way to test for allergies is via skin pricks. Skin tests offer greater accuracy because they are more sensitive than blood tests. They also give results within 20 minutes, are less expensive and allow for broader testing,” says Albany-based allergist Manisha Relan.

Sitesh Roy, an allergist and immunologist based out of Mumbai, shares another advantage that skin tests offer. “With a skin test, an allergist can design the exact test necessary and tailor-make the test panel based on the patient’s country, region, exposures or diet. With blood tests, patients undergo a standard panel of tests that might not be country- or region-specific,” he says. Blood tests, Roy adds, can also frequently reveal items that aren't a cause for concern. “In the case of a blood test, multiple positives which are not always relevant is a common problem,” he says. Kothari expresses similar apprehensions about blood tests. “About 50 to 60 per cent of all allergy blood tests give false positive results. It could show that you’re allergic to a certain food, if you’ve eaten it just before taking the test,” she says. The opposite, explains Damania, could also occur. “If you’re allergic to something but haven’t consumed it for a long time, it may not show up in your results,” she says.

The way forward

However, even the most accurate allergy tests only play a supporting role, and while they are an important aspect of the process, decisions should never solely be dictated by them. “A careful history and examination before and after the test are invaluable and absolutely necessary to identify which positives, on a skin or blood test, are clinically relevant and causative of the patient’s symptoms. A positive test is only indicative of sensitisation. If symptoms are involved, then it’s an actual allergy,” says Roy. Relan is aligned with this school of thought. “Clinical history is everything. I like guessing what the environmental trigger for a patient will be based upon when, where, and how they react. It can give significant clues to one’s trigger, which is then confirmed by testing,” she says.

In some cases, supervised exposure to triggers may also be advised. “It can be helpful to find a correlation between the test and what disagrees with you through trial and error. For example, in the case of mild allergies, if you strongly suspect that you’re allergic to peanuts, you can avoid peanuts for a week or so and then reintroduce it in a small quantity to see if it’s causing a reaction. However, if you have a severe allergy, you probably know about it already. You would’ve seen a reaction when the food was first introduced in your diet as a child,” says Damania. With food and drug allergies, Roy also finds that allergen avoidance and re-introduction can be effective in combating any persisting confusion. “Sometimes, further studies, under an allergy specialist’s guidance, are much needed to figure which positives are worth avoiding and which ones are not causing problems,” he concludes, reinforcing that while allergy tests offer useful insights, they may often not be as helpful if considered in isolation.

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