This is the first episode in our Conversations on Food Allergy podcast series, and Dr. Edwin Kim discusses the differences between a food allergy and a food sensitivity, how one can be tested and diagnosed, and the current research in this field.
Dr. Kim is an Assistant Professor of Medicine in the Division of Rheumatology, Allergy, and Immunology and the Thurston Arthritis Research Center. Dr. Kim is an allergist who sees patients in the UNC Allergy and Immunology Clinic, and he directs the UNC Allergy and Immunology Fellowship Training Program as well as the UNC Food Allergy Initiative.
“The testing can be by skin or by blood, and one benefit of the skin test is it takes about 15 minutes and we’ll have a result at that visit, as opposed to a blood test which can take several days to get that result. A lot of times there is a lot of anxiety around food allergy, so I think being able to give that answer pretty rapidly is helpful.”
– Edwin Kim, MD, MS on food allergy testing
Ron Falk, MD: Hello, and welcome to the Chair’s Corner from the Department of Medicine at the University of North Carolina.
Today we start a series of conversations on food allergies. We will hear from UNC experts who specialize in food allergy treatment and research. Today’s episode we’ll discuss food allergy and food sensitivity: what’s the difference? How can one be tested and then treated? Where is the current research and where is this field headed?
We welcome Dr. Edwin Kim who is an Assistant Professor of Medicine in the Division of Rheumatology, Allergy, and Immunology and is part of the Thurston Arthritis Research Center. Dr. Kim is an allergist and he sees people in the UNC Allergy and Immunology Clinic, and he directs the UNC Allergy and Immunology Fellowship Training Program as well as the UNC Food Allergy Initiative. Welcome, Edwin Kim.
Edwin Kim, MD: Thank you.
Falk: We’re going to be talking about food, which is a real passion of mine, food allergies and food sensitivity. I also realize that you’re going to be testing me for food allergy so I think that’s going to be an interesting experience.
Kim: I hope so. Our field of allergy is very much visual so hopefully going through this test will show you what it is and hopefully allay some of the concerns or fears that people may have about coming in to see an allergist.
Differences Between a Food Allergy and a Food Sensitivity
Falk: Help me understand the difference: what is a food allergy, and what’s a food sensitivity? They sound similar, but they’re clearly different.
Kim: Sure. Over the last 5-10 years there’s been some confusion because the terms have been all interchanged. Thankfully, over the last couple of years there’s been much more of a consensus on how to describe these. The way I usually describe this to my patients is that there are all kinds of things that can happen to you from eating a food, and only a small subset of those would be considered an allergy. When we’re thinking about allergy, I’m thinking about a specific reaction that happens in your immune system after you eat a particular food—it might be shellfish, it might be peanuts, or even red meat. What this immune reaction could actually do is ultimately lead to a constellation or a group of symptoms that can even be as severe of what many people have heard of as anaphylaxis and be life-threatening.
On the other side, there are many other symptoms that people can have after they eat foods that don’t lead to anaphylaxis or aren’t life-threatening. More recently these have all been termed together as food intolerances or food sensitivities. The difference there is the mechanism that is causing that to happen – is not always going to be the immune system, and actually most of the time is not the immune system. And the consequences of that, if it’s going to be life threatening, for example, those results are going to be very, very different. I do walk people through that because it is very confusing on what we’re exactly talking about.
Falk: If you realize that there’s a food that just doesn’t make you feel good, that would be more of a sensitivity?
Kim: I would ask a few more questions to get more details on that. Sometimes for even food allergies, these immune reactions that can lead to anaphylaxis, they can start out as just being uncomfortable with the food. A simpler way might be to start with how we define food allergies and then everything else.
When I’m thinking about food allergic reactions potentially leading to anaphylaxis, this can be a combination of symptoms all over your body. The one that most people are probably most familiar with are symptoms on your skin. You could have red, itchy bumps that look like mosquito bites or hives— or welts is the term that some people use, and they can be around the mouth or they can be all over the body.
Some people can even have swelling that happens from this. Swelling of the lip or the eye, probably the most frightening is swelling of the throat which can make it difficult to swallow or breathe. Symptoms in your stomach are very common with the allergy type. You can have horribly crampy abdominal pain to the point where you are buckled over and can barely function. A lot of times this can lead to vomiting as well, and even diarrhea as the reaction progresses. Another category of more scary type of symptoms are related to breathing. Folks who have asthma will recognize these exact symptoms—it can be a sense of tightness in your chest, where you just can’t get that deep breath, that shortness-of-breath feeling. Sometimes it’s just uncontrollable coughing or a wheezing sound that comes. The concern there would be that it ultimately can lead to not being able to breathe at all.
Falk: How quickly do those symptoms occur after one has eaten something?
Kim: They typically occur very rapidly. The medical term we use for this whole group of reactions is “immediate-type hypersensitivity” – the term immediate is the important thing here. Very often for most patients, within 10-15 minutes they’re going to start having symptoms. Occasionally it can take a little bit longer, maybe up to an hour or two, possibly because there’s a lot on the stomach and it’s taking longer to absorb. Most people, it’s going to happen during that meal, while they’re still there, and sometimes people are going to be excusing themselves to the restroom and discover that they’re covered in these rashes or other things like that.
Falk: That’s a different phenomenon than the symptoms of someone who has a sensitivity.
Kim: That’s correct.
Falk: What are the differences?
Kim: Time is definitely one of those – in general with allergies, the symptoms are going to happen rapidly, within 15 minutes.
Sensitivities – it’s hard to generalize because it’s a combination of a lot of different types of things causing reactions, but most of those you think of taking a lot longer, sometimes a couple of days, to show up. For a lot of these food intolerances and sensitivities people are describing, the symptoms mostly are happening near the stomach area, but usually you don’t have a lot happening on the skin— you don’t have this itchy rash that I described, or the swelling, and most of the time you won’t have the breathing problems – chest tightness or shortness of breath. Around the stomach a lot of patients will have a crampy pain, very often they may have a mix of either feeling constipated or having diarrhea as well. It does seem like a lot of symptoms focused there. What’s also different about sensitivities is that they have less physical symptoms— a feeling of being exhausted, another term I’ve heard patients describe is “brain fog.” It’s a sense that they can’t think straight and can’t really function. There’s a lot of other symptoms that can potentially come with this, but the physical symptoms revolve around the stomach.
Top Foods Associated with Allergy & Sensitivity
Falk: If you were to name the foods that are the most common causes of allergy, which ones are those?
Kim: There are eight groups of foods that we think of as accounting for pretty much all of food allergy, about 85-90% of the anaphylactic type allergy – that’s going to include milk, egg, wheat, soy, peanuts and tree nuts, as well as fish and shellfish, and of all of those, milk, egg, wheat and soy, as well as peanut, most of those show up in childhood. The shellfish is a much more common thing to show up in adulthood. Another difference in those allergies of milk, egg, wheat, and soy—thankfully most of those resolve on their own in childhood, whereas the peanuts, tree nuts and seafood, unfortunately tends to linger for most of people’s lives.
Falk: What are the common foods associated with sensitivity?
Kim: The most common one that we see in our clinic is gluten, and that’s where it can be confusing because wheat is also on that list I just described as food allergies. When folks come in with concerns about gluten, very often they’ve done some reading on their own ahead of time. It’s a nice conversation I can have with them about what we know and what we don’t know about wheat.
Two diseases in particular that are pretty well-described in the medical literature and in the lay press, are celiac disease and anaphylactic wheat allergy. Celiac disease is inflammation in your gut that leads to injury in your gut every time you have gluten products, and leads to watery diarrhea and can lead to weight loss. That is clearly diagnosed by your gastroenterologist when they’re able to do an endoscopy and look inside. There are some blood tests that try to predict whether the patient has it, that endoscopy, although it is invasive, is the best test for that.
Then the anaphylactic reaction we just described as well–hives and swelling. Most of the patients don’t have either – and for a long time we struggled with, “What is going on here?” All of these patients were coming in telling us, “Every time I eat gluten I have these with feelings—my stomach is cramping, I’m having diarrhea, I’m having constipation, I’m gaining weight—I can’t go in to work. I can’t even function at work.” Like a lot of these newer diseases, when you first hear it, you think, “I don’t know what this is, it doesn’t fit into either of the categories.” But when you start to see patient after patient with sort of the same complaints, you start to wonder, “Maybe there’s something going on here. What is this?” Over the past few years, people embraced this to try to start to understand it better. The first step toward this is really giving it a name. What you start seeing in the literature is “non-celiac gluten sensitivity” or “gluten intolerance.” I think, although it’s sort of a wishy-washy name, it is a really important step that has to happen, that way people can all focus on the same thing and try to understanding what’s going on here.
Falk: Other than gluten, are there other major causes of food sensitivity?
Kim: We have a lot of patients coming in talking about different types of fruit that cause problems, sometimes it’s very acidic type of fruits that cause rashes around the mouth area or symptoms that are more severe.
Falk: Have you heard about chocolate?
Kim: Unfortunately, I’ve heard about chocolate, the good news for most people it is not a life-threatening reaction. Some folks have significant symptoms, mostly stomach symptoms or some symptoms around the mouth can come with that as well.
Food Allergy Tests
Falk: The way to figure out whether one is allergic or sensitive to one of these food groups is with an allergy test. How good are those?
Kim: It can be very good but I think it’s important to understand what it does and does not tell us, and that’s sometimes where people can get tripped up. We have allergy testing that can be done in two different ways—one of them is by skin test, which I hope you’ll be able to do today, and we can get it through the blood as well. What both tests are trying to do is actually find that part of the immune system, this antibody called IgE, that causes these allergic reactions. These tests try to tell us, “Yes, it’s there” or “No, it’s not there.” Again, what we know, and this is where it can get tricky, we know that having the antibody by itself does not necessarily mean you’re going to have an allergic reaction—but if you have someone who has told you a story that sounds very much like allergy and then you can prove that they have this, a positive test, when you combine that story it makes it pretty clear that they do have allergy.
If you’d like I can walk you through that procedure right now.
Falk: Absolutely. For purposes of folks listening, Dr. Kim has a whole allergy testing kit here, and my arm no longer has a shirt over it, and he has an alcohol swab and I’m going to be allergy tested, although I’m not sure I have any food allergies.
Kim: We’ll test you for a couple of foods that are on the list that I described—one will be for peanut and one will be for wheat, and we’ll have two controls. One of those controls definitely should become itchy, and I’ll walk you through what that will look like, and one of those should not become itchy as our negative control, which will be plain salt water which no one should have a problem with. I mentioned before that the testing can be by skin or by blood, and one benefit of the skin test is it takes about 15 minutes and we’ll have a result at that visit, as opposed to a blood test which can take several days to get that result. A lot of times there is a lot of anxiety around food allergy, so I think being able to give that answer pretty rapidly is helpful.
Falk: Okay, here goes.
Kim: I’m opening an alcohol swab and I’m just going to clean you off, because I don’t want to introduce anything on your skin underneath your skin. I’m actually going to use a pen and give you a brand-new tattoo, Dr. Falk, this is strictly just to label and make sure there’s no confusion. Now as you can see on my tray, within this tray we have liquid versions, basically purified extracts of foods and pollens you might be concerned about. There is a plastic pricker that’s inside there. I think it’s important to keep in mind that this is not a needle. A lot of patients when they think about coming to an allergist one thing they think about is being stuck by a needle. What we do is a special test using a skin prick or percutaneous—the idea is just to scratch the surface of the skin, so there should be very little if any pain that comes with this. So let me go ahead and do that right now.
Falk: So I have a brand-new tattoo, and I’ve just had a nice little skin prick which you can hardly feel at all. Truly a pricking little motion. Didn’t even know it happened. I think the most exciting part is now I have a series of letters written on my arm as a temporary tattoo.
Kim: In the clinic setting, the next thing I would do is distract you, to not think about it. Occasionally it can be itchy and we don’t want you to scratch it and mix all of the tests together. We can talk a little bit more about foods, but over the next fifteen minutes I’ll keep a close eye to see what is happening on your skin and whether there is a reaction that may happen there.
Risks of Continuing to Eat a Problem Food
Falk: Let me come back to this issue of the vagaries of food sensitivity or even food allergy. If someone has a really mild reaction after eating a certain food, even if that happens on a number of occasions, is there a risk for that person continuing to eat that food?
Kim: Here again it becomes very important to differentiate between food allergy and then the intolerances and sensitivity. For food allergy, the reactions can be unpredictable—the patient can have 9 times in a row a reaction to peanuts and just had mild stomachache and mild rash, but then the tenth time could be a full-blown anaphylactic reaction. So for food allergy there can be a risk for continued exposure. In that case, once the diagnosis is made, it would be about strict avoidance.
Falk: If someone has a shellfish allergy, if they have a reaction once or twice, they should stay away from shellfish.
Kim: That’s exactly right, because it is unpredictable. The last thing we would want is a life-threatening reaction to happen there. For intolerances, generally speaking, we’re talking about multiple different types of foods at once, most of those are not going to be life-threatening, and at this point we don’t know if they will be progressive—meaning getting worse as you eat them more. In general, for most of my patients, if they can tolerate the small amounts, I’m okay with that, but I do have them continually reassess where they are. If it’s affecting their regular daily activities, I need to have a conversation with them about the risks and benefits of continuing to do this.
There is more and more research in food sensitivity to understand what is happening in the actual gastrointestinal tract, and we may find out that a small amount is not safe. As tolerated is important. Avoidance is very difficult—things are better these days because foods are labeled better, but remembering to ask questions everywhere you go, to find out if there could be contamination is difficult. Then simple cost—unfortunately we’ve discovered with gluten-free foods, although many more are available now, they cost tremendously more. All of this could add up to making quality of life worse, not better.
Using Epinephrine and Responding to Anaphylaxis
Falk: If someone has an anaphylactic reaction or really looks like they’re allergic–let’s use shellfish as the example. There are things called EpiPens that provide epinephrine which you can get as a prescription—they’ve been in the news lately because they cost so much money—when do you give a prescription for an EpiPen?
Kim: Anyone in my mind who has the anaphylactic reaction should have an EpiPen. Thankfully, fatal food reactions are really rare, perhaps there are a couple hundred of these per year, and that’s out of about 15 million people who have food allergy. Fortunately, the testing that I described earlier, and that you’re going through right now, Dr. Falk, can tell us a little bit about the probability of a reaction, but we don’t have any good tests that can tell us severity, so we can’t really predict who these people are, which is one of the inherent problems of food allergy—we have all these folks out there who are worried that that next ingestion could lead to something terrible, but within those few people who do have life-ending or fatal food reactions, one of the themes that comes over and over again is not using their epinephrine soon enough.
Epinephrine really should be the first medicine that people are thinking about in an allergic reaction. I think for most people, Benadryl or an antihistamine like that is usually what they think of. What we know with the Benadryl is that very often it’s slow—it can take anywhere from 30-45 minutes to work. Allergic reactions can really progress quickly, as I described to you before, it can take from 5-10 minutes for it to start. You can imagine if you’ve taken your Benadryl at the restaurant and you’re waiting, it can really lead to a lot worse. Having that epinephrine–but having it in your pocket is not good enough. If you are having symptoms that are rapidly progressing—over a 10-minute period you go from having a couple of hives on your face to covering you from head to toe, and you’re vomiting, or if you have anything that’s affecting your breathing—swelling in your throat, or difficulty talking or swallowing, or having tightness in your chest—for the majority of patients out there, you’re not going to be wrong to use epinephrine. Some cases it may be overkill, but it’s better to keep you safe than to start too small and potentially get yourself in big trouble.
Falk: It’s probably wise if you’re having one of these allergic reactions not to run to the restroom, for in fact, you could run to the restroom and run out of the reach of people who could help you.
Kim: Yes, being around folks, and if this is severe enough someone should be calling 9-1-1 to make sure you get immediate help.
Falk: That’s where the problems have been with people who want to cover up that they’re having an anaphylactic reaction, they need to be publicly calling for help, in addition to using the EpiPen.
Kim: Yes, there are many stories I’ve seen in my clinic of exactly that, where people are embarrassed in a social situation and not be feeling right, and like you said, disappearing into the restroom and potentially not coming back.
Falk: Which is very different than the reaction to a food sensitivity where the process is so much slower.
Diagnosing Vague Symptoms & a Food Elimination Diet
Falk: Imagine that the person who’s listening is having vague symptoms—they’re not entirely sure why, just listened to your word choice of “brain fog,” and have fatigue or perhaps there is intermittent and perhaps food-related prompts with nausea. How do you determine whether someone who has these vague symptoms that aren’t clearly associated at all with eating, how do you know whether this is or is not a food sensitivity or allergy?
Kim: In general, when we think of food allergy—and I explain this to patients—your immune system is not going to choose whether you have a good day or a bad day. If you are allergic, a reaction should happen most of the time, if not every time you are exposed. By virtue of that, when you have adults coming in to clinic, most of them have been eating many of the foods in question for quite a while without having a life-threatening or anaphylactic reaction. So by default, for many of the patients I see, I’m automatically thinking, “Could this be some form of food intolerance or food sensitivity?” So I start with a conversation about the timing and the symptoms—if there’s enough concern that this potentially could be anaphylactic or food allergy, I go through exactly what we’re doing with your arm right now this skin test, or a blood test, at the very least to rule that out. If there’s a food allergy, we’re talking about strict avoidance, epinephrine and really thinking about 9-1-1 if you get into this.
Then with the sensitivities, here it’s much more difficult, because at this stage there really isn’t great research on what is happening here. Folks are starting to do that by lumping all the patients together under this term “non-celiac gluten.” I think they’ve been able to gather patients to find out what might be happening, but I’m not aware of any blood test, immune test, anything like that, that can be diagnostic of this. It probably makes sense because we don’t even know the mechanism, we don’t know why in the world this is happening. At this point, diagnostic testing is very difficult, so what we end up doing is basically a food elimination and a reintroduction diet.
Falk: Let’s describe a food elimination diet—what do you do?
Kim: Through the conversation, we try to find out what the highly suspected food may be. For many patients, it will be gluten. We would start with one food at a time, trying to change as little as possible, but the idea there would be reading every single label for everything they’re eating and try to strictly avoid this food. Typically, in my clinic I’ll say for a minimum of two weeks but many folks will advertise up to four to six weeks strictly avoiding this and no cheating at all, and then just to continue to the monitor the key symptoms that they’re having, so whether they’re related to the stomach or the fatigue or otherwise. It’s not a perfect test, but there what we’re looking for is a very, very obvious improvement, if not a complete cure of the symptoms.
Falk: The outside timeframe there is four to six weeks?
Kim: Typically, yes, about four to six weeks—again, easier said than done for sure, especially for gluten especially which is just prevalent everywhere. That part a lot of patients are on board, and many patients are already doing when they come to see me. But what takes a lot of convincing from me, is then to reintroduce it. So, “Okay, you’re not eating it now and all of these symptoms have gotten much, much better, and you’re just happy. And then I’m going to tell you to eat 10 bagels and see what happens!” The looks that I get from patients are exactly the look that you just gave me, of disbelief, “What are you saying? I just got better. Why?” The thought there would be by reintroducing if we actually do see the symptoms come roaring back—it’s not a perfect test, but it gives us a little more confidence of, “This is the real trigger here and I’m not avoiding the food ‘just because,’ there really is a connection.” Now can I say for sure after that test that it absolutely is a gluten intolerance, there is a mechanism, whether immune or otherwise? I can’t say that, but again I think it gives us more reason for the avoidance.
Falk: Patients should trust their own instincts, in other words, if they’re not feeling well. What’s the information like out on the web that folk can look at? If you look online you see all sorts of interesting and complicated and faddish diets. What you’re describing is a very simple elimination, but on the web there’s all sorts of information. Where do you tell people to look, and how to filter what is out there?
Kim: I do want to quickly talk about the diets—you mentioned the faddish diets, and that is something that is complicating the whole picture. There are a lot of gluten elimination type of diets out there and a lot of people do feel better from those type of diets—perhaps from better nutrition, perhaps from being more aware of what they’re eating, or whatever it may be. It seems to muddy the water for folks who have the non-celiac gluten sensitivity. The diets, not necessarily bad, but it does confuse things that are out there. Like you said, there is a lot of information out there, and if you look hard enough you can probably find almost anything you want on the Internet.
Typically, what I tell patients is to focus on the big medical sites that are out there—MedScape or WebMD—probably the areas where people run into the most trouble are the personal blogs–folks who have made themselves self-made experts. I don’t think these folks are making anything up, I think they’re absolutely telling their own story, but the problem is their story may not line up with most people out there, and I think that’s the piece that sometimes gets lost. If some folks want to look at this just for reassurance of “I’m not alone,” I don’t fault patients for that at all. Patients are advocating for their own health. I do very much try to educate them as much as I can on what we do know on food allergies and sensitivities, and guide them to these major sites.
Current Research in Food Allergy & Sensitivity
Falk: Where’s this field going? What research are you doing, and what are other folks doing that really will help inform food sensitivities in particular?
Kim: Most of our research is focused on the allergies, and through that in another way we learn more about the sensitivities. But unfortunately for the food allergy landscape, from all these years, the last 30, 40 years, there’s been a tremendous increase in the number of food allergies and intolerances being diagnosed, but sadly to this point, we still just don’t have a treatment.
One of the things that our group, in the Food Allergy Initiative with Dr. Burks, is looking at, is there a way to reverse or protect people against these anaphylactic reactions? The general term for this is immunotherapy but the simple way I explain to people, is taking small amounts of what they’re allergic to—whether it’s wheat, peanut, or shellfish, and give them small increasing amounts of it. The goal there is to try to find an amount that’s big enough that your immune system sees it, but not big enough that you have an allergic reaction–really just to build that immune system up against it.
Then we try to not only do that, because we think in the short term that is a good protection, but then we try to keep them on that dose for an extended period of time with the hope that we’re actually able to retrain the immune system and perhaps even turn off that allergy. We’ve done that in a few different ways so far–one is oral immunotherapy and that is as simple as taking something you’re allergic to and eating small amounts of it. In our research setting that’s in the form of flour, so peanut flour or egg flour, but strictly because it’s a research thing. Most recently what we’ve looked at is a couple different ways we can do this—one of them is called sublingual. What we have is very similar to what we tested you with, liquid extracts of some of these foods, that we give some drops underneath the tongue, and hold that for two minutes per day, with the idea of trying to expose the immune system and retrain it.
Falk: Mucosal immunity.
Kim: That’s correct—and the final way we’ve been studying is epicutaneous, essentially a medicine patch, it’s the newest and has been quite exciting on the idea that maybe you don’t even have to go near the mouth. A medicine patch you put on your body once a day—if that can somehow get to your immune system and retrain it, that would be amazing. All three of these approaches we’ve been involved in here at UNC, and what’s really exciting for the field, is that for the first time ever, we have a couple of products that are seemingly very close to reaching the hands of patients. Two companies–one of them is taking the oral immunotherapy product and one of them is taking the epicutaneous, and they’re in Phase III at this point with the FDA. The hope is that in the next couple of years we’ll see some positive data.
Dr. Falk’s Food Allergy Test Results
Falk: That would be just wonderful. Okay, so I can report that of the four spots that I have on my arm, there’s one that’s clearly red for sure, but not bad. I think you’re going to measure it.
Kim: Right—from the bird’s eye view, I can say this is great news, because the two foods that we cared about, look just like the salt water, which means no reaction at all. You do have the one raised itchy bump, which looks like a mosquito bite, and that’s supposed to happen to show that your skin does react to the histamine. I’m going to use my ruler and just measure the size of that bump—it looks like the width of the bump is about eight millimeters, and that’s important to me because that tells me that the test did work well. If you had a bump for any of the foods, I would do exactly the same thing for measuring that bump. Anything that is three millimeters or wider would be considered a positive, and concerning because then you would have the IgE antibody that could lead allergic reactions.
Falk: The other ones just look exactly like the salt water control. They’re completely flat and sort of boring looking.
Kim: Right. You can go back to having your peanut butter sandwich on wheat.
Falk: On wheat toast, exactly right! This has been an interesting on-the-air example of how an allergy test occurs and I am none the worse for wear. That has been a fun experience. Dr. Kim, thanks for much for participating in this podcast.
Thanks so much to our listeners for tuning in. If you enjoy this series, you can subscribe to the Chair’s Corner on iTunes or like the UNC Department of Medicine on FaceBook. In our next episode, we’ll discuss peanut allergies with one of the world’s experts in this field, Dr. Wesley Burks. Thanks so much for listening.