There are a variety of these at-home testing kits. Some advertise that they can detect a person’s food allergies, whereas others say they can detect food intolerances or sensitivities. Can you explain the differences between those terms?
That’s a question we get all the time. As allergists and immunologists, we have a very narrow definition of “allergy” because our evaluation is really looking for anaphylactic food allergies, where food causes severe, life-threatening allergic reactions. For example, when a kid eats a peanut and they break out in hives and have difficulty breathing, that is classified as a peanut allergy, and they need epinephrine to treat that reaction.
Other types of reactions, such as digestive issues, are not fatal, but they can cause a lot of discomfort. In general, many non-medical people will define food allergy as any food that causes a symptom. A person with celiac disease, for example, may say that they’re allergic to gluten or wheat, but that is much different than an anaphylactic food allergy. Yet, they need to avoid wheat or else they’ll have symptoms, and that’s where the water gets murky when it comes to sensitivities and intolerances versus allergies.
A textbook example of intolerance is lactose intolerance. This is where you can’t digest milk sugar, and it causes a lot of issues like flatulence and diarrhea if you do. Whereas for food sensitivities, people usually identify specific foods that cause symptoms. For instance, someone may find that they can eat pasta without experiencing any symptoms, but a burger bun from a certain restaurant does trigger symptoms.
In general, do you think at-home food allergy or food sensitivity tests are accurate?
Although some of these tests may be effective in giving patients results, there is a lack of substantial data to support whether these tests are accurate for a large number of patients. I’ve seen patients who have reported doing an at-home test and have spent hundreds of dollars, but after eliminating the foods the test recommended, their symptoms are still not any better.
For an at-home food sensitivity test that collects blood samples, many of those companies are usually looking at immunoglobulin subclass 4 (IgG4) antibodies. These are the same antibodies that represent a normal immune response to gut bacteria and foods. The company often uses an algorithm to assess your levels and give you a list of foods you may potentially want to eliminate. This can result in people greatly limiting their diet, perhaps needlessly.
Not all companies are the same. Some of these food sensitivity tests have some science behind them. There are at-home immunoglobulin E (IgE) food allergy tests that are certified by the federal Clinical Laboratory Improvement Amendments program, for instance. I would be more skeptical of other companies that, for example, ask for a sample of your hair to test your reaction to certain foods and chemicals.
What is the typical process you follow to test if patients are allergic to certain foods?
What we are trying to identify is anaphylactic food allergies, because if you eat it, there’s a chance you could die from it. A typical food allergy will present within 15 minutes to two hours of ingestion. People often experience hives, low blood pressure, high heart rate, and difficulty breathing. Other symptoms may include acute nausea, vomiting, and profound smooth muscle contractions.
The biggest concern that a lot of folks have is with the throat, or wheezing. Sometimes people will ingest foods and there will be these mimics, such as acid reflux that affects your upper airway, and so in our clinic, we try to sleuth out these reactions. We may do a prick test, which exposes the skin to the substance suspected of causing an allergic reaction, or a blood test to determine if you’re allergic to something.
We typically don’t see false negatives in allergy testing. If the test comes back positive, it doesn’t necessarily mean that you’re allergic to the product; it means you have a sensitization to it. For instance, some adults who were allergic to eggs when they were children have since grown out of their allergy, but they may still test positive for it. It requires the right symptoms plus the testing to equal an allergy.
The gold standard of diagnosing a food allergy is to do a food challenge by having a person consume food we suspect they may be allergic to while we monitor them. If we see the start of an allergic reaction, we can treat it promptly.
What are the common foods you see reactions to?
The common food allergies are to peanuts, tree nuts, sesame, fish, shellfish, milk, eggs, wheat, and soybeans. Occasionally, we’ll see an oral allergy syndrome where, for example, a person will experience throat scratching in response to foods like berries and melons, but the interesting thing is that if you cook that food completely, that reaction goes away. For instance, some people cannot eat fresh strawberries, but they’re able to eat strawberry jam.
Are food allergies on the rise?
Food allergy is becoming a more common diagnosis. Is that because of microbiome influences, antibiotic exposures, maternal factors, or something else? The jury is still out on that, but we do know that it is increasing and there are likely a number of factors contributing to it.
We also don’t exactly know why food intolerances and food sensitivities exist. It may be a complicated interplay of microbiome influence of your gut, the fact that food is processed in different ways, the additives in foods, and so on. There are lots of variables that are not controlled and haven’t been studied.
How often do you have patients request an allergy test because they experience symptoms like a scratchy throat after eating a certain food?
That is a lot of our patients, and most will say, “I had a question about this food. Is this something I need to be concerned about?”
If symptoms are suggestive of food allergy — hives, discomfort or irritation in their mouth, nausea, vomiting, wheezing, etc. — then skin testing may be helpful. If the symptoms are not consistent with food allergy, then food elimination may be helpful. For those people, I may recommend they do food eliminations one trigger at a time to assess whether eliminating a certain food affects how they feel. But if a person eliminates foods and it makes them feel worse or negatively affects their nutrition and weight, then we may want to conduct testing.
Could cutting out certain foods unnecessarily have any potential downsides or harms associated with it?
There are potential harms if you needlessly eliminate foods. For instance, there could be psychological harm if you go to a restaurant, list your sensitivities, and then the restaurant is not accommodating. Or maybe, because of your dietary restrictions, it’s now harder to go out with friends and colleagues to restaurants.
You may also negatively affect your health if you are eliminating a huge part of a normal, healthy diet, such as by removing lots of fruits or vegetables.
Could needlessly eliminating a food lead to developing an allergy to that food? That's the theoretical risk — to what extent that actually exists, it's not quite well known. For example, if a person needlessly cuts out milk from their diet, they may theoretically develop an allergy to it. This may be more of a concern in patients who have allergic sensitization or other history of allergies than in patients who don't have these risk factors.
Overall, what would you most like for the public to know about these at-home testing kits?
If you are interested in these kits, just be an informed consumer. Understand what it’s trying to tell you and what you, as the consumer, want to get out of the test. In my experience with patients who have taken these tests, it generally has not been helpful to them. That being said, there may be others who have found benefits to this, but we don't have large studies to support it.
Feel free to ask your health care providers about this as well, whether it’s your primary care doctor, your pediatrician, or allergists like me. We can always do testing if somebody’s really interested. I’m happy to talk to patients about what they’re going through so that they feel heard. I want them to feel empowered about the next steps they need to take to manage their symptoms.
