The Science Behind Allergy Diagnostics

When it comes to diagnosing food allergies, there are two tests that healthcare providers typically turn to: skin-prick testing and specific IgE (sIgE) blood testing. On the surface, both seem fairly simple. But have you ever wondered what these tests are actually measuring? And how, exactly, they aid in the diagnosis of a food allergy?

Well, you’ve come to the right place. Refresh your beverage, log out of Twitter, and settle in as we present a deep dive into the science behind allergy diagnostics. Things might get a little bit complicated, but we promise we’ll make the ride as smooth as possible.

We’re going to let you in on a secret: To really understand allergies and how they are diagnosed, we need to discuss the immune system. Yep. That immune system. The one you use to fight colds, flus, and everything in between.

Let’s start with something called Immunoglobulin E (IgE).

What is allergic sensitization?

People who produce elevated sIgE that can recognize a specific allergen are described as being “sensitized” to the allergen. Having an increase in sIgE is correlated with an increased likelihood of having an allergic reaction when exposed to that allergen.

But sensitization doesn’t guarantee that the person will definitely have an allergic reaction. In the case of food allergies, it also doesn’t indicate that a food should be completely removed from a patient’s diet, especially if the patient is currently eating the allergen without problems.

At the molecular level, IgE antibodies don’t actually react to whole foods. There is no alarm screen that says “WARNING: PEANUT” or “INTRUDER DETECTED: EGG.” Instead, IgE antibodies are recognizing, and interacting with, small fragments of each allergen. In the diagnostic world, these fragments are called allergen components.

We know what you’re thinking. “What are allergen components?” We’ll tell you!

Component tests vs. whole allergen tests

Now that you know what allergies have to do with the immune system, it’s time to reveal how component tests differ from whole allergen tests. 

In a whole allergen test (commonly done with skin prick testing or via blood testing), all of the “puzzle pieces” are present in the test. That means it’s impossible to determine the specific component to which a patient with a positive result is sensitized. Why does that matter? Remember when we talked about peanuts, eggs, and milk? And how being sensitized to one protein and not the others could impact the patient’s life? Only component testing can identify which specific proteins or molecules may be triggering reactions. As more and more of these components are identified, and new tests become available, people can gain more knowledge about their specific “allergic fingerprint,” and this can help them better manage their allergic disease.   

By understanding patients’ allergies at the molecular level, healthcare providers can help patients better understand their allergies and identify patients who are the best candidates for an oral food challenge.²  Diagnostics are powerful tools, but ultimately a patient’s physical response to consuming a potential allergen is the only way to truly rule an allergy in or out.³

So … that’s it?

Phew. That was a lot, but you made it.

While we can’t give an exam to measure how well you retained the information (nor do we want that pile of paperwork), we do want you to feel empowered and informed so that the next time your healthcare provider mentions diagnostic testing, you’ll have a better understanding of why the test is valuable, and what it measures. Just remember that you should always discuss your test results and allergy management plan with your healthcare provider. They are the true experts in creating personalized allergy diagnosis and allergy management plans.