Food Allergy and Sensitivity Testing: What You Need to Know

You have a hunch that certain foods are behind your symptoms - maybe the bloating after meals, the headaches, the skin flare-ups, or the fatigue that never quite lifts. But how do you actually confirm which foods are the problem? And once you start looking into testing, the options can feel overwhelming.

Not all food reaction tests are created equal. Some are medically validated and highly reliable. Others are more controversial, with debate about what they actually measure. Understanding the landscape helps you make informed decisions about which path makes sense for you.

Testing for True Food Allergies

If you suspect a genuine food allergy - the kind involving an immediate immune response that could potentially be severe - there are well-established testing methods.

Skin Prick Testing

This is one of the most common allergy tests. A small amount of the suspected allergen is placed on your skin, usually on your forearm or back, and the skin is lightly pricked so the substance enters just below the surface. If you are allergic, you will develop a small raised bump (similar to a mosquito bite) within about 15-20 minutes.

Skin prick tests are quick, relatively inexpensive, and results are available immediately. However, they can produce false positives - meaning the test shows a reaction, but you do not actually experience symptoms when eating the food. This is why a positive skin test often needs to be interpreted alongside your actual experience with the food.

Certain medications, particularly antihistamines, need to be stopped before testing as they can interfere with results. People with severe eczema may not be good candidates for skin testing.

Blood Tests (IgE Testing)

Blood tests measure the levels of IgE antibodies your immune system has produced in response to specific foods. Higher levels suggest an allergy, though like skin tests, elevated IgE does not always mean you will have symptoms when eating the food.

Blood tests are useful when skin testing is not possible - for instance, if you cannot stop antihistamines or have extensive skin conditions. They are also used to monitor allergies over time to see if they might be resolving.

The limitation is similar to skin testing: a positive result indicates sensitization (your immune system recognises the food), but does not guarantee you will react when you actually eat it.

Oral Food Challenge

This is considered the gold standard for diagnosing food allergies. Under medical supervision, you consume gradually increasing amounts of the suspected food while being closely monitored for reactions.

Oral food challenges are the most definitive way to know whether a food actually causes symptoms. They are typically done when other test results are unclear, when there is reason to believe an allergy may have been outgrown, or when the stakes of avoiding or not avoiding a food are high.

Because reactions during testing can potentially be severe, oral food challenges must be conducted in a medical setting with emergency equipment available. They are time-consuming but provide the clearest answers.

Testing for Food Sensitivities

Here is where things get more complicated. Unlike true allergies, food sensitivities do not involve IgE antibodies, and there is no universally accepted medical test for them.

IgG Food Sensitivity Panels

These blood tests measure IgG antibodies to various foods. Many functional medicine practitioners and alternative health providers offer them, and they can test reactions to dozens of foods at once.

The interpretation of IgG testing is controversial. Some practitioners find them clinically useful - clients often feel better when they avoid foods that show elevated IgG levels. However, mainstream medical organisations generally do not recommend them, arguing that IgG antibodies are a normal response to eating foods and do not necessarily indicate a problematic reaction.

If you choose to do IgG testing, it is worth understanding this debate. The results may provide useful starting points for exploration, but they should not be taken as definitive proof that a food is causing your symptoms. Eliminating every food that shows elevated IgG can lead to unnecessarily restrictive diets.

The Elimination Diet

For identifying food sensitivities, an elimination diet remains one of the most reliable methods - despite being lower-tech than blood tests. The process involves removing common trigger foods (typically gluten, dairy, eggs, soy, corn, and sometimes others) for a period of three to four weeks, then systematically reintroducing them one at a time while carefully monitoring symptoms.

The elimination diet works because your body tells you directly whether a food is a problem. When you remove a problematic food and symptoms improve, then symptoms return upon reintroduction, you have clear evidence of cause and effect.

The challenge is that elimination diets require commitment, careful planning, and attention to detail. Symptoms from reintroduced foods can be delayed by hours or even a day or two, so you need to reintroduce foods slowly and keep good records. Working with a practitioner who can guide the process often makes it more successful.

Mediator Release Testing (MRT)

This specialised blood test measures chemical mediators (like histamine and cytokines) released by white blood cells when exposed to various foods. The idea is that this captures a broader range of reactions than IgE or IgG testing alone.

Some practitioners find MRT useful for creating targeted elimination protocols. It is not as widely validated as traditional allergy testing, but for people struggling with complex or unclear food reactions, it can provide additional data points.

What About Intolerances?

Food intolerances - like lactose intolerance - are digestive issues rather than immune reactions. Testing for these is different.

Lactose intolerance can be confirmed through a hydrogen breath test, where you drink a lactose solution and your breath is analysed over several hours. Elevated hydrogen indicates that lactose is being fermented by gut bacteria rather than digested properly.

Similar breath tests exist for fructose malabsorption and small intestinal bacterial overgrowth (SIBO), which can cause reactions to certain fermentable carbohydrates.

Making Sense of It All

With food reactions, no single test tells the whole story. The most reliable approach often combines testing with careful observation of your own body.

If you suspect a true allergy (immediate reactions, potentially severe), see an allergist for proper evaluation. Safety matters here.

If you suspect sensitivities (delayed, vague, or chronic symptoms), consider starting with an elimination diet. It requires more effort than a blood test, but it gives you direct information about how your body responds to specific foods.

Whatever testing you do, pay attention to how you actually feel. Tests provide data, but your lived experience is the ultimate measure of whether a food works for you or not.

And remember - food sensitivities are not always permanent. Often they develop when gut health is compromised. As you address underlying gut issues, you may find that foods you once reacted to become tolerable again.

Looking for the next step? Explore natural approaches to managing food reactions or learn about the different types of food reactions.