Episode transcript
Time stamps
0:19 Intro and the importance of differentiating intolerance vs. allergy
1:51 Defining food allergy and understanding its mechanisms
2:52 Celiac disease vs. food allergy
3:56 The different types of food Intolerance and their mechanisms
4:30 Metabolic Intolerance
5:41 Pharmacologic Intolerance
7:54 Toxic Intolerance
8:34 Overlap between food allergy and food intolerance
9:43 The clinical insignificance of at-home IgG food intolerance tests
11:01 Professional guidelines against IgG food intolerance testing
11:42 Tips on educating patients about allergy vs. intolerance
12:23 Using serological IgE testing to differentiate and diagnose food allergy
13:49 Understanding two types of patient misconceptions
15:37 Recommendations on how to approach patient conversations on food reactions
Transcript:
Announcer:
ImmunoCAST is brought to you by Thermo Fisher Scientific creators of ImmunoCAP™ Specific IgE Diagnostics and Phadia™ Laboratory Systems.
Gary Falcetano:
I'm Gary Falcetano, a licensed and board-certified PA with over 12 years experience in allergy and immunology.
Luke Lemons:
And I'm Luke Lemons with over six years experience writing for healthcare providers and educating on allergies.
You're listening to ImmunoCAST, your source for medically and scientifically-backed allergy insights.
On today's episode of ImmunoCAST, we're going to be diving into food allergies and food intolerance and what the difference is between those as well as how patients may interpret some of their symptoms as
maybe an allergy when they're really an intolerance because adverse reactions related to food are very common.
Gary Falcetano:
Food allergy or adverse reactions to food not only are very common, but patients are looking for answers, and they're certainly using all of the resources available to them, including the internet, including at-home testing, and we're going to talk about all of that.
Luke Lemons:
And just on those tests, they use IgG. We'll dive deeper into it later, but it's really not recommended for allergy diagnoses. But as you're saying, Gary, the patients are Googling their symptoms, and they're getting targeted by ads for these types of tests.
So we want to go through a few of the intolerances that often get confused with allergy to better help even, as a provider, narrow your differential diagnosis because you may have patients who are experiencing these sort of symptoms, and it's important to always look at history and understand these symptoms before going into using testing.
Gary Falcetano:
Exactly. And these are real symptoms, right, so we need to acknowledge that patients are experiencing issues and really help them work through getting to the bottom of their diagnosis.
Luke Lemons:
Exactly.
So why don't we go into first looking at what is a food allergy? So a food allergy is a type one hypersensitivity reaction involving IgE antibodies which cause a cascade, causing histamine and other mediators to be released.
Gary Falcetano:
Exactly. We know you have to have a sensitization first, right? You have to be sensitized and produce those antibodies. And then on subsequent exposures, those antibodies cross-link and release these mediators, and there are symptoms that are closely correlated with IgE-mediated reactions. We know that typically these reactions are rapid onset, so they happen quickly after the ingestion of a food. They're usually reproducible under similar circumstances. Every time you ingest that food under similar circumstances, you have a similar reaction. And we also know that food allergy is a spectrum. There's a spectrum of symptoms that can occur on ingestion, everything from very mild isolated symptoms to systemic symptoms and even anaphylaxis.
Luke Lemons:
And it's not anaphylaxis or nothing when it comes to food allergy. We often think of food allergy, and we think of the epinephrine auto injectors, but symptoms can vary and that's why there's often confusion in this overlap between whether it's allergy or whether it's something else. So another immune-mediated disorder but is not an allergy is Celiac. So this doesn't involve IgE. It is not an allergy. Some patients may think that they have a wheat allergy when they have a Celiac autoimmune disorder, but that's just not the case. Celiac is an autoimmune disease. Histamine is not released when a patient eats, let's say, bread.
Gary Falcetano:
And working through the differential of adverse reactions to wheat or gluten can be a little challenging, so we can have IgE-mediated wheat allergy, we can have autoimmune Celiac disease, we can have non-Celiac gluten sensitivity, which is having symptoms associated with ingestion of gluten or wheat but not having IgE antibodies and not having the markers for Celiac disease.
Luke Lemons:
And so those are the two immune-mediated reactions that we wanted to go through, food allergy and Celiac. One is an allergy, food allergy, obviously in the name, and then Celiac is an autoimmune. But looking at intolerance, food intolerance is a reaction that does not involve the immune system. It's not immune system mediated. And we can break food intolerance down into, let's say, three major etiologies.
Gary Falcetano:
There are certainly more than this, but I think the three major ones are metabolic, pharmacologic, and toxic.
Luke Lemons:
And in metabolic we see that these sorts of reactions are due to a patient lacking an enzyme that is needed to digest that food. It's one of the causes for this metabolic intolerance. So lactose intolerance, fructose intolerance, patients may have symptoms in their GI because they don't have an enzyme that helps break down, let's say, lactose in this example.
Gary Falcetano:
Exactly. It's very common for patients just to equate any symptoms related to a specific food like an apple with fructose intolerance or milk product with lactose intolerance and just call it an allergy. But in true terms, yes, they're having symptoms, but these are not IgE-mediated, they're not going to have anaphylaxis from these.
Luke Lemons:
There's actually another interesting metabolic intolerance, and this involves when somebody drinks alcohol and their cheeks begin to flush.
Gary Falcetano:
And this is pretty common in patients of Asian descent, and it really comes down to the inability to break down or process ingested alcohol, and this is a deficiency in the aldehyde dehydrogenase-II enzyme or ALDH-2 enzyme that Asian patients can be genetically predisposed to.
Luke Lemons:
Yeah, it's just another interesting metabolic intolerance, but looking forward into the next type of food intolerance, pharmacologic, this is a sort of intolerance that comes from somebody reacting to a chemical, let's say, something that isn't toxic on their own that most people or most patients may not react to, but they do. So for example, caffeine, MSG, these are examples of a sort of intolerance.
Gary Falcetano:
Yeah, exactly. And some people have difficulty metabolizing histamines, so they have symptoms when they ingest food that are high in histamines. Things like red wines, certain fruits, cured meats, cheeses.
Luke Lemons:
And speaking of cheese, there's actually another pharmacologic intolerance which is termed as the cheese effect.
Gary Falcetano:
So this one is an interaction between MAO inhibitors reacting with tyramine that's found in certain cheeses. I think we probably all remember back from some of our Board questions, this is a common, what reacts with MAO inhibitors or what precautions do you have to take? And this is a pretty severe effect of a severe hypertension related to the MAO inhibitor interaction with tyramine.
Luke Lemons:
And this amino acid is commonly found in cheese. And in fact, when it was first isolated, it was from cheese and later named after the Greek word for cheese, which is tyros.
Gary Falcetano:
Luke, usually I get to do these fun facts, but I'm telling you, you're keeping me on my toes here. So tyramine comes from the Greek for cheese. Okay, I like it.
Luke Lemons:
Yeah, I know. Who would've thought that that was the origin of this amino acid, was from cheese. But another sort of food intolerance that somebody could have is toxic. So this is like food poisoning, E. coli. When people say that they get food poisoning, it's a food intolerance.
Gary Falcetano:
Yeah, exactly. And we've talked about this in previous episodes, but also scombroid, fish poisoning, and this isn't an allergy to fish, but an allergy to, well, for lack of a better term, bad fish. So as the fish begins to age or decompose, it produces histidines. When we ingest them, we convert them to histamines, and we have symptoms that look just like allergy, not allergy at all, just a reaction to bad fish.
Luke Lemons:
Pharmacologic, toxic, metabolic. These are all food intolerances because they don't involve the immune system. They're not immune mediated, and they're not IgE mediated as well. Again, the IgE is very important, so patients may experience these symptoms because there is some symptom overlap between food allergy and these intolerances. They may go online looking for help, and they may book an appointment with you to figure out why they're experiencing these sort of symptoms. And it's important to narrow a differential diagnosis through looking at history and then using serological testing.
Gary Falcetano:
Yeah, exactly. And before we go a little more in depth on the testing, we should mention IBS, right? A very common diagnosis, really pretty much a diagnosis of exclusion. I mean, there is the Rome criteria, right? We know what defines IBS, but it really is ruling out other things such as IgE-mediated allergy such as Crohn's Disease, inflammatory bowel diseases. There was recently a position paper or a clinical guideline from our gastroenterologist colleagues that speak to really needing to rule out alpha-gal sensitization in patients with IBS.
Luke Lemons:
Let's actually talk about patients who maybe have Googled their symptoms and bought in a food intolerance test online and decided to take it. For all the reasons above, it's important to know that, again, intolerances are not allergies, but so it may be more common for patients to use the word allergy synonymous with their symptoms of intolerance. And so somebody may say, "I'm allergic to kiwi and banana and apple because I took one of these intolerance tests, and they all came back positive." But these tests don't utilize IgE.
Gary Falcetano:
Well, exactly. And we know in order to diagnose a clinical allergy, you must have symptoms that are consistent with clinical allergy, correlate that with positive sensitization to IgE, and then correlate the two to make the diagnosis. Unfortunately, Luke, these tests are promoted quite heavily on social media. They're very common for patients who are looking for answers to have these presented to them as a potential answer for their adverse food reactions, and we know that these are marketed as food intolerance tests or food sensitivity tests, but there's not a whole lot of evidence that they really provide us much of anything.
Luke Lemons:
They use IgG, which has its place in medicine, but not to diagnose an allergy or even an intolerance. In fact, the European Academy of Allergy and Clinical Immunology reported that these sorts of tests, which
examine IgG, are irrelevant for the examination of food allergy or intolerance and, "should not be performed in the case of food-related complaints."
Gary Falcetano:
Both of the major allergy organizations in the U.S., the College and the Academy of Allergy, as well as the World Allergy Organization, all have pretty strong statements against these IgG tests and conclude that they shouldn't be used in the diagnosis of food allergy of any form.
Luke Lemons:
And so a patient goes online, they get this test because they've been experiencing symptoms, and they do it. They find out they're positive or have elevated levels, let's say, to chicken, and now they think they have a chicken allergy. They may come to you and to your office during, let's say, like a physical, and they say, "Hey, I found out that I'm allergic to chicken this past year because I got one of these tests." And so providers here, you have an opportunity to really help educate these patients on what is an allergy and what is not as well as really getting to the bottom on why they felt the need to do this sort of testing. What kind of symptoms were they experiencing that they weren't able to find relief from?
Gary Falcetano:
Exactly. And then by working through the differential diagnosis, right, figuring out if this truly is a clinical allergy with IgE sensitization, doing that by serologic IgE, specific IgE testing, or in the absence of that when that's proving to be not the case, then working through some of these other non-IgE-mediated, potentially nonimmune-mediated issues that can cause these symptoms that the patients have presented with.
Luke Lemons:
And we have a great episode on diagnosing food allergy from recent guidelines from the European Academy of Allergy and Clinical Immunology. So definitely check that episode out. And we also have an episode right before this that was about the state of allergies and patients in the U.S. And it really, it's related here because they're trying to find relief. They're really trying to find relief where they can, and sometimes these testing kits are where they see a shining light, but in reality it doesn't help them in any sort of way and spreads almost misinformation about their own health.
Gary Falcetano:
Exactly. And we talk about all the time, Luke, how important clinical history is, and those European guidelines have an excellent section on how to do a structured food allergy history, and that can really guide next steps. So if the symptoms are synonymous with clinical allergy, then what specific IgE testing should be done to confirm or rule out clinical food allergy?
Luke Lemons:
So keep in mind when a patient does come in, there's maybe two types of patients that are the focus of this conversation of food allergy versus food intolerance. There's a patient who comes in and says, "Hey, I'm allergic to this." Again, that word allergic is used so commonly, but they come in, they say, "I'm allergic to this because I'm allergic to milk because I had a glass of milk and my stomach hurt." Narrowing your differential diagnosis and helping them is a very important step into figuring out what about the milk "made it hurt."
Gary Falcetano:
Going back to that, doing a well-thought-out food allergy history for sure.
Luke Lemons:
Yes. And then utilizing serological specific IgE testing to confirm or to rule out allergy as the role, and then just working to make sure that patients can manage their symptoms.
Gary Falcetano:
Yeah, we've discussed in the past how sensitive specific IgE testing is. So when we get a negative, it's very reassuring that that's not the cause of the patient's symptoms or certainly not a clinical allergy related to those symptoms.
Luke Lemons:
So we have those patients who diagnose themselves without any sort of testing and are coming to their provider for answers. And we also have another type of patient who has maybe already conducted the IgG food intolerance test and felt that they've gotten the answers that they needed, but that is not true.
Gary Falcetano:
This interaction with them can be potentially thorny. You don't want to kind of negate everything they've done, but I think it's important to give them the best evidence-based information around what a true clinical allergy is and how it's diagnosed.
Luke Lemons:
And these patients might have not even come into the office looking for answers around their symptoms because they've eaten a certain type of food. This could come up at a yearly physical when asking what has changed in the past year, and they say, "Well, I did a test at home, and I'm allergic to XYZ." That's, a little siren should go off and be like, "Oh, what were your symptoms?" Because they may be avoiding something that they don't need to avoid, and there may be better ways to manage their symptoms, but we don't know what's actually causing them. They did an at home IgG food intolerance test.
Gary Falcetano:
Yeah. If they've done this IgG "food intolerance test," I think it's important to let them know that this cannot in any way diagnose a clinical allergy number one, and actually there's very little evidence that
these are even a good indication of any food intolerances. And of course, doing that in a way that isn't off-putting to the patient or paternalistic, but still allows them to get the best information.
Luke Lemons:
The episode right before this was all about how patients may feel right now with allergies as well as this population health information around allergies in the U.S. It's really interesting. We'll link to that on this episode's webpage. You can find in the description of this episode a link there. We'll also include on the topic of education an article that is for patients. It's patient facing from our friends at Allergy Insider, and it's about food intolerance tests and food allergy tests and food allergy and food intolerance, and it breaks it down in a way that may be beneficial when these patients do come in, and you're trying to really let them know that maybe a different type of testing is the answer.
Gary Falcetano:
I think it would be really helpful for those patients and takes the focus off the clinician and brings in a third party to bring them that information.
Luke Lemons:
Exactly.
Also, on this webpage for this episode, we'll have a link to a lab ordering guide where you can find the test codes for food allergens from your local labs that you've already probably used based on your zip code.
So thanks for listening to ImmunoCast, and don't forget to share and subscribe for more allergy related medical insights.
Gary Falcetano:
Thanks so much. We'll see you next time.
Announcer:
ImmunoCAST is brought to you by Thermo Fisher Scientific, creators of ImmunoCAP™ Specific IgE diagnostics and Phadia™ Laboratory Systems.
For more information on allergies and specific IgE testing, please visit thermofisher.com/immunocast.
Specific IgE testing is an aid to healthcare providers in the diagnosis of allergy and cannot alone diagnose a clinical allergy. Clinical history alongside specific IgE testing is needed to diagnose a clinical allergy. The content of this podcast is not intended to be and should not be interpreted as or substitute professional medical advice, diagnosis, or treatment. Any medical questions pertaining to one's own health should be discussed with a healthcare provider.
