IgG tests promise to reveal food sensitivities. But are they science or science-ish?

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At-Home Food Sensitivity Tests Vs. Food Allergy Tests

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You might be disappointed to learn that a food sensitivity test is unlikely to explain your GI symptoms. Here, we discuss whether you may want to consider taking a food allergy test instead.

Figuring out if specific foods are causing unwanted symptoms is a complicated process, as food sensitivities are still not well understood. And, so far, no food sensitivity panel can accurately and definitively diagnose food sensitivities.

Food allergy tests, however, may provide information about foods that are potentially dangerous for you.

We'll explain what we know about food sensitivities and why food allergies can be easier to diagnose. We also explore what else may be going on if you think your symptoms might be related to a specific food.

In short: No. There's limited evidence to support using a food sensitivity test at home.

Many of these tests measure your body's immune response to a variety of foods by testing the levels of certain antibodies in your blood, such as IgG and IgG4, after you're exposed to various food antigens.

Yet 2016 research suggests that the presence of these antibodies may not be an accurate or reliable marker of food sensitivity, especially because many other antibodies and cell-mediated reactions may also be involved in food sensitivities.

What's more, many of the studies that companies cite to support using these tests are outdated or have been published in unreputable journals.

Some tests claim to help you understand how your body may respond to certain foods based on factors such as your genetic background. However, the research is limited surrounding genetic testing and food allergies and sensitivities.

Multiple organizations, including the Canadian Society of Allergy and Clinical Immunology and the American Academy of Allergy, Asthma & Immunology (AAAAI), have advised against using these tests to diagnose food sensitivities.

Notably, food sensitivity tests are not a replacement for a personalized care plan from a doctor or registered dietitian.

David D. Clarke, board certified gastroenterologist and president of the Psychophysiologic Disorders Association, explains that many GI symptoms incorrectly attributed to food sensitivity can be caused by conditions including irritable bowel syndrome, inflammatory bowel disease, gallstones, and peptic ulcer.

If you experience symptoms, including hives, itching, and swelling after eating certain foods, it's important to rule out food allergies, which can be quite serious. In some cases, food allergies may lead to anaphylaxis, which can be life threatening.

Doctors commonly use certain tests to diagnose food allergies:

Skin test: This type of test involves pricking your skin with a probe that contains a small amount of food allergen and monitoring your reaction.

Blood test: This test helps determine whether you are allergic to specific foods by measuring the amounts of certain antibodies in your blood.

Oral food challenge: This procedure involves consuming small amounts of a suspected allergen under the supervision of a doctor. They will keep emergency equipment and medication on hand in case of a severe reaction.

19% Of Adults Think They Have Food Allergies, How Many Really Do?

Since she was six years old, Shoshana Blumenfeld, 11, has avoided eating carrots, several kinds of... [+] fruits, tree nuts, and peanuts because of a misdiagnosed peanut allergy. Now that a new test has revealed she is only allergic to birch pollen, Blumenfeld can eat almost anything she wants. (Photo by Tamir Kalifa for The Boston Globe via Getty Images)

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Things aren't always what they seem with life, love, and food allergies.

Food allergies aren't as clear cut as, say, explosive diarrhea. Very few people think that they have explosive diarrhea when they don't. The reverse is true as well. You tend to know when you have explosive diarrhea, so being oblivious to the "explosions" may be a bit unusual. By contrast, as a study just published in JAMA Network Open showed, food allergies remain very misunderstood and potentially "misunderestimated" and "misoverestimated" at the same time.

For the study, a team from Northwestern University (Ruchi S. Gupta, MD, MPH, Bridget M. Smith, PhD, Jialing Jiang, BA, Jesse A. Blumenstock, BS, Matthew M. Davis, MD, MAPP, Robert P. Schleimer, PhD), the University of Southern California (Christopher M. Warren, BA), and Stanford University (Kari C. Nadeau, MD, PhD) analyzed responses from 40,443 adults in the U.S. To Internet and telephone surveys conducted from October 9, 2015, to September 18, 2016. Survey questions asked respondents about what food allergies they had, their symptoms, and what testing and medical attention they had received. The team then classified the identified food allergies as "convincing" or "non-convincing", based on the responses.

They found that 10.8% of the respondents currently had one or more "convincing" food allergies, well below the 19.0% total who reported having food allergies whether they were "convincing" or "non-convincing." In other words, only about half of the people claiming food allergies seemed to provide enough backing evidence. Of course, the researchers did not follow around and test each of the 40,443 adults, which would have been really, really time consuming. Therefore, they had to base their assessments purely on the survey responses.

Here a girl gets tested for allergies. (Photo By BSIP/UIG via Getty Images)

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Do these results convince you that many "food allergies" may not be real food allergies? Before you become a doubting Thomas, or Tammie or Tilapia or whatever your name may be, about all food allergies, look at the flip side of this situation. The study also found that many people with real food allergies hadn't gotten official physician diagnoses. Less than half (47.5%) of the convincing crowd had actually been diagnosed by physicians as having food allergies. This makes you wonder how many people have food allergies without knowing it. After all, unlike explosive diarrhea, you may not realize that you have a food allergy until you get a more severe obvious reaction. Maybe that funny feeling that you thought were nerves is actually a food allergy. Or how about those unexplained gastrointestinal symptoms for which you've been chugging antacids? That difficulty breathing that you thought was love? Perhaps, it is just all that peanut butter that he or she smears on his or her face. Then, there are those weird skin rashes that you simply tried to cover up with make up or clothing.

Thus, there seems to be major mismatches regarding food allergies in general. It may be that not enough people are seeing their doctors and using real medical science to address potential allergies. There are a lot of food allergy claims, theories, and treatments floating around the Internet. A Google search reveals a number of chiropractic clinics offering advice and services regarding food allergies A research letter published in BMC Allergy, Asthma & Clinical Immunology by Timothy Caulfield, LLM, LLB, and Christen Rachul, PhD, from the University of Alberta found that 42-45% of the websites for naturopathic clinics in Alberta and British Columbia, Canada, offered "allergy testing" and 47%-60% offered "allergy treatments." The question is how many of these claims and treatments are actually based on scientific evidence.

At the same time, there may not be enough real medical doctors addressing or considering food allergies. When is the last time that your doctor discussed food allergies in depth with you in between staring at the computer screen and trying to squeeze everything else into a 15-minute window? Plus, some people may not even have access to or be able to afford a doctor who can adequately cover food allergies. In fact, the study found that those who had annual incomes of less than $25,000 were significantly less likely to have a physician-diagnosed food allergy.

Suzanne Franklin suffered from extreme food allergies for years - and doctors warned her that... [+] pregnancy would make the allergies worse. So she found an unusual solution. She found that she wasn't allergic to Mcdonald's Big Macs - so she ate a Big Mac burger every day throughout her pregnancy. (Photo by Worldwide Features / Barcroft Media / Getty Images)

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Moreover, much remains unknown about food allergies. They can be very serious and even life-threatening, as the study revealed that a little over half (51.1%) of those with "convincing food allergies" had experienced at least one severe allergic reaction. They can really hinder and alter your daily life. In the study, the 5 most common culprits for "convincing" food allergies were shellfish (reported by 2.9% of the adults), peanuts (1.8%), milk (1.9%), tree nuts (1.2%), and fin fish (0.9%). You may think that "not being shellfish" may be easy, but avoiding peanuts, milk, and tree nuts can be quite a challenge. Think about how many packages have the warning "made in a facility where there were nuts."

Additionally, many aspects of food allergies need better explanations. For example, why did the study find racial and ethnic minorities to be more likely to have "convincing" food allergies, with Asian-Americans 28% more likely and Black Americans and Hispanic Americans both 20% more likely than White Americans? Then, there were the gender differences, with women being 67% more likely than men.

With our food supply becoming more complicated and more chemicals and other additives in our food and our environment in general, expect the food allergy issue to just grow more and more complex. As a National Academies of Medicine report indicated, evidence suggests that food allergies have been on the rise for the past two decades, but experts still don't know why. Some of it may be growing awareness of food allergies. But that probably doesn't explain all of it. More studies and science are needed. And if you have unexplained symptoms or are concerned about having a food allergy, see a doctor to get tested for allergies, a real doctor and not someone who is allergic to science.

Food Allergy Testing 101: When It's Necessary And How It Works

A doctor can diagnose food allergies using a variety of tests, including skin prick tests, blood tests, and oral food challenges. Home test kits are also available, though they have several downsides and aren't widely recommended.

Food allergies affect around 4% of children and 1% of adults worldwide. Food allergies are more common in Western countries, like the United States, and seem to be on the rise.

Keep reading to learn more about what food allergies are, who should get tested, and how food allergy testing works.

While countless foods can cause allergic reactions in some people, the Food and Drug Administration (FDA) currently lists nine foods as major food allergies, including:

Symptoms of a food allergy may start shortly after ingesting the food, or they may be delayed for a few hours. Common symptoms of a food allergy include:

swelling of the tongue, mouth, or face

red, itchy bumps on the skin (hives)

itching of the lips and mouth

wheezing

stomach pain

nausea, vomiting, or both

diarrhea

a life threatening reaction known as anaphylaxis

If you or your child have symptoms of a food allergy, consider looking into food allergy testing. There are several ways to test for food allergies, including skin prick tests, blood tests, and oral food challenge tests. Doctors often use a combination of these methods to ensure an accurate diagnosis.

Most food allergies develop early in life, during childhood. Yet they can develop at any age, which means a food allergy could develop during adulthood. A food allergy will trigger some sort of symptom every time you eat the food or foods to which you're allergic.

Keep in mind that food allergy symptoms can vary in severity, and you may not have the same reaction every time you eat a food you're allergic to.

If you suspect you or your child may have a food allergy, it's critical to visit a healthcare professional, like an allergist, to undergo appropriate testing.

Several types of tests are commonly used to diagnose food allergies, including skin prick tests, blood tests, and oral food challenges. Here's a closer look at each.

Skin prick tests

After taking a detailed personal and family history, healthcare professionals typically use a skin prick test first when trying to diagnose a food allergy.

In general, skin prick tests provide a rapid means to detect food allergies and are cost-effective.

What to expect

Skin prick tests involve placing a small amount of liquid extracts of certain foods on your skin, usually on your back or arm. Next, the healthcare professional uses a small tool to lightly prick your skin, allowing some of the food extract to get below your skin's surface.

They may also test for nonfood allergens, such as pollen. This is because people allergic to pollen can also experience an itchy mouth and throat after eating certain fruits and vegetables, such as apples or kiwis.

The reaction occurs because the proteins found in these foods are similar to those found in pollen, which can confuse the immune system. Allergists refer to this as oral allergy syndrome or pollen fruit syndrome.

After 15–20 minutes, they'll examine the area for any signs of an allergic reaction, such as bumps or a rash.

Considerations

Though a positive test result indicates the possibility of reactivity to a food, it doesn't necessarily mean you have a food allergy. In fact, up to 60% of positive skin prick tests do not reflect symptomatic food allergy. So your doctor may have to use other tests, like an immunoglobulin E (IgE) blood test, to rule out or diagnose a food allergy.

Skin prick tests also aren't appropriate for everyone, including people who:

have certain skin conditions

are taking certain medications

are at an increased risk of having a serious reaction to skin prick testing

Blood tests

An allergy blood test measures the amount of IgE in your blood. There are two types of allergy blood tests:

Total IgE test: measures the total amount of IgE antibodies in your blood

Specific IgE test: measures the amount of IgE your body produces in response to a single type of allergen

Your healthcare professional might perform an allergy blood test after a skin prick test or when they cannot perform a skin prick test.

Blood tests may also be preferred over skin prick tests in young children, as skin prick tests may be too uncomfortable for them.

What to expect

To do a blood test, a healthcare professional will take a small sample of your blood and send it to a laboratory. In the lab, the sample will be exposed to different foods.

If your blood releases a lot of IgE antibodies in response to a particular food and you have symptoms when you eat that food, you're likely allergic to it.

Considerations

Unlike skin prick tests, which yield quick results, blood test results can take several days to get back. The test is also usually more expensive than a skin prick test, though some health insurance plans will cover the cost.

As with skin prick tests, blood tests can produce false positives. You may need to follow up with an additional test in the weeks or months after the initial one.

Oral food challenges

If skin pricks and blood tests don't produce clear results, your healthcare professional may have you do an oral food challenge. This is generally done in a doctor's office under close supervision, as it can sometimes cause a severe allergic reaction.

An oral food challenge is considered to be the most reliable and definitive food allergy test because it provides quick results that are easy to identify.

This test is also helpful for adults looking to find out whether they still have a food allergy from their childhood. For example, allergies to milk, eggs, wheat, and soy often resolve with age.

What to expect

To prepare for an oral food challenge, suspect foods are typically eliminated from the diet for 7 to 14 days before the challenge. This increases the likelihood of a definitive result. You must discontinue medications that could interfere with the results, such as antihistamines and b-adrenergic bronchodilators, before oral food challenge tests.

During an oral food challenge, you'll be given a small amount of food while your doctor checks for signs of a reaction. If you don't have a reaction, they'll gradually increase the amount of food. If you don't have a reaction to this larger amount, you can likely rule out a food allergy.

If the test result is negative, your healthcare professional will rule out a false negative with supervised feeding using a typical serving of the food in question. A false-negative oral food challenge result can occur in 1–3% of cases.

If an oral food challenge does detect a food allergy, you will have to completely remove the allergen from your diet to avoid allergic reactions.

Considerations

Unlike skin prick or blood tests, oral food challenges require avoidance of suspect foods for 7–14 days leading up to the test. Additionally, you could experience a severe allergic reaction during testing.

Yes, there are a variety of at-home food allergy kits you can order online or purchase in drugstores.

Most kits have you prick your finger and send a blood sample off to a laboratory. Other kits require sending in a sample of your hair. After analyzing your sample, the company will give you your test results.

At-home food allergy tests aren't generally recommended

Despite their widespread availability, many healthcare professionals do not recommend at-home allergy tests because of concerns about safety and reliability.

For example, most tests are based on outdated and questionable research and use controversial methodologies.

Food allergy testing generally relies on seeing whether your blood produces IgE antibodies in response to certain foods. But most home tests only measure immunoglobulin G (IgG) antibodies.

There's no evidence that this can help diagnose a food allergy. In fact, according to the American Academy of Allergy, Asthma, and Immunology (AAAAI), the presence of IgG in the blood is a typical immune response to food exposure, and having higher levels of IgG antibodies to specific foods may actually indicate tolerance, not an allergy.

A 2022 study found that just 1 of 22 food allergy test kit companies used an accredited laboratory, performed IgE testing, and had a clinician involved in the testing process. All of the other companies used unaccredited laboratories and controversial, unreliable testing methods.

It's also worth noting that while at-home tests may seem less expensive than a doctor's visit, most insurance plans don't cover at-home test kits. Because of this, your out-of-pocket cost may be higher with at-home tests, depending on your coverage.

There's no cure for food allergies, and the only treatment is strict avoidance of the offending allergen or allergens.

You must be aware of products that contain the food or foods to which you're allergic and be diligent about reading ingredient labels and making food workers, such as waiters, aware of your food allergy.

If you're allergic to multiple foods or are unsure of what products contain ingredients that might trigger an allergic reaction, it's recommended to work with a healthcare professional who specializes in food allergies, such as a registered dietitian or allergist.

They can help you identify products that contain allergens and develop an allergen-free, nutritionally complete eating pattern.

Your healthcare professional may prescribe medications, such as epinephrine and antihistamines, which people at risk for developing anaphylaxis should carry at all times. These medications are used in case of accidental exposure to an allergen and can save your life if you experience allergic symptoms such as throat swelling, shortness of breath, and low blood pressure.

In addition to providing medical advice and prescribing necessary medications, your healthcare professional can answer any questions you may have about how to keep yourself safe and healthy while living with a food allergy.

What is the best way to test for food allergies?

An oral food challenge test is considered the gold standard of food allergy diagnosis. It's sometimes used to confirm a suspected food allergy. However, since this test may trigger life threatening reactions, it should be administered by trained healthcare professional in a medical setting only.

Are food allergy tests worth it?

Allergy tests administered by trained healthcare professionals are the safest and most accurate way to diagnose a food allergy. Allergy experts do not recommend at-home food allergy testing kits, as most use controversial and ineffective testing methods.

Food allergies can cause potentially serious reactions, so it's important to get properly tested if you think you might have a food allergy. While home test kits offer tempting convenience, they aren't very reliable.

Work with a doctor or other healthcare professional to help confirm whether you have a food allergy. They can also help rule out other causes of your symptoms, such as a food intolerance or sensitivity, which are different from an allergy.

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