Why Food Allergies Are on the Rise

Brigid Bergin: It's The Brian Lehrer Show on WNYC. Welcome back, everybody. I'm Brigid Bergin filling in for Brian today. You may have noticed in recent years that menus and restaurants across the city and elsewhere are coming with a lot more information about potential allergens. Even along your grocery store shelves, items are labeled dairy-free, soy-free, peanut-free. If you've got a kid in school, there are so many brands that make classroom-safe treats that ensure there is no trace of any of those irritants. Peanut butter is frequently forbidden in schools due to so many severe allergies.

It's not just marketing. Food allergies are on the rise, having doubled in children between 2000 and 2018 according to the CDC. There isn't a comparable data set for adults, but other research tends to say the same. Why are we so allergic all of a sudden? Andrew Van Dam, who writes the weekly Department of Data column for the Washington Post recently crunched the data on the question and what's behind the uptick in kids and adults alike. He joins us now. Andrew, welcome back to WNYC.

Andrew Van Dam: Thank you so much.

Brigid Bergin: We're also joined by Christopher Michael Warren, Assistant Professor of Preventative Medicine and Director of Population Health at Northwestern University's Center for Food Allergy and Asthma Research. That is a mouthful. Dr. Warren, welcome to WNYC.

Christopher Michael Warren: Thank you. My pleasure to be here. Thank you so much.

Brigid Bergin: Listeners, we need you to be part of this conversation. Have you personally experienced a new, maybe unexpected food allergy for yourself or in your family? When did you first notice the change, and did you know it right away or did you have to hunt it down through a tough allergy investigation, going to one of those doctors and doing one of those panels? What was that like? Anyone out there really allergic to something as a kid but now you aren't? How do you know? Do you just have a question for one of our allergy experts? You can tweet @BrianLehrer, or give us a call at 212-433-WNYC. That's 212-433-9692. You can also text us at that number.

Andrew, that stat, wow. Allergies have doubled in children between 2000 and 2018. What are we seeing kids react to?

Andrew Van Dam: Well, the most common food allergies in kids, and Christopher can speak to this better than I can, tend to be milk, first of all, and then peanuts. That changes as we become adults of course, when milk allergies tend to drop a little bit and things like shellfish rise.

Brigid Bergin: Dr. Warren, do you want to pick up on that at all?

Christopher Michael Warren: Sure. He summarized it pretty well. I would say that there does appear to be this real preponderance of cow's milk allergy very early in life. Cow's milk, actually, according to the data that we've managed to amass over the past decade, appears to actually be the most common allergy in infants and kids until age five, at which point peanut assumes the throne. As kids enter adolescence and often following development of allergies to things in the environment like pollen, dust mites, things like that, other allergens shellfish then become more common. Shellfish is absolutely the most common allergy among adults. It just depends on what age you are, what you're most likely to have if you are food allergic.

Brigid Bergin: Dr. Warren, can you just break it down for us? What exactly is a food allergy and what are the range of reactions people can experience that would confirm they have a food allergy? Certainly, we know people who carry EpiPens and that would be one example, but it's not always as extreme as that. Correct?

Christopher Michael Warren: Yes. Just to add a little extra layer of complexity on top of all of this, there are lots of different types of food allergies. They have different mechanisms. Some are what we call immune-mediated most frequently through this type of antibody called IgE. It's those IgE-mediated food allergies that I think most people have in mind when they think about that kid carrying an EpiPen who has a peanut allergy or who has a shellfish allergy.

That said, there are a lot of other types of allergies that also appear to be on the rise maybe even more rapidly than some of these IgE-mediated food allergies. Those are things like FPIES, or food protein-induced enterocolitis syndrome, which is what happens when you might have infants who are vomiting very profusely after being exposed to things like milk, or oat, or things like that. That's a whole different mechanism that we don't quite understand but is also important when thinking of the whole world of food allergies.

Brigid Bergin: We're going to go to Lisa in Westchester County. Lisa, thanks for calling WNYC. I understand you had an incident with a food allergy.

Lisa: Yes, I did. About five years ago, I was actually getting loose stools for a few months. I did see a gastroenterologist. They had given me a medicine called Xifaxan or Rifampin. I took it for a couple of weeks. It came back, took it a couple of weeks, came back and again, and then the gastro doctor advised that I should take this medicine for four weeks straight. I did and at that point, I suddenly developed an allergy to every single food I ate. Within 20 to 30 minutes, and I don't have any food allergies at all, my hands would turn bright red, my face would turn red, and I developed cramps in my hands, in my knees, and literally, arthritic bumps on my hand joints.

I went to see 10 doctors, immunologists, rheumatologists, gastroenterologists. I was checked for every food allergy possible. They couldn't figure out anything. I had colonoscopies, endoscopies, and the gastroenterologist I was seeing at the time recommended I try something called EnteraGam, which is an immunoglobulin powder. You mix it in in water. She said, take that three times a day for a week and see what happens. Within a week, my reaction to food cut itself within half.

Brigid Bergin: Wow.

Lisa: Then I went to see a rheumatologist. He gave me sulfasalazine for which for the past five, six years, I'm taking 300 milligrams a day since to stop this abnormal reaction. The conclusion it might be is that the Xifaxan changed my microbiota to the point where I developed leaky gut, and it was as almost as the food was leaching itself out into my bloodstream, creating this abnormal reaction.

Brigid Bergin: Oh my goodness. Lisa, thank you for sharing your experience. Dr. Christopher Michael Warren, is that type of story something you've heard before?

Christopher Michael Warren: I'm going to be honest and tell you no. I think, thankfully, most individuals who I know and who we study with with food allergies do not experience symptoms as wide-ranging and as ubiquitous as those. I realized, I neglected to actually answer the question you asked me before, which is what are the typical signs and symptoms of food allergic reaction. I'd be happy to clarify those.

Most folks, in contrast to what we just heard from the caller, who have a food allergy, they experience things like hives, things like local swelling around the locations that the food touches. That's because there's a local immune reaction where your immune system is recognizing these proteins that it's taking in. Then it has, based on some previous exposure, decided to classify these proteins as something that is harmful to the host, harmful to us as a human body and therefore expedite the process of getting that the heck out of there.

That's how you end up with things like vomiting, things like diarrhea, things like coughing, wheezing. They're all processes that the body has evolved very helpfully over time with the purpose originally of expelling parasites and microorganisms like roundworms and things like that, that used to be absolutely ubiquitous. Almost every single person on the planet at some point would have these in their bodies. We have this very helpful immune response to try to get rid of them that now our immune system is bringing to bear on some of these other far more innocuous substances.

Brigid Bergin: Andrew, you write that "boys and girls are equally likely to have food allergies, but as both age past puberty, food allergies among women grow much more common, especially in middle- age. What might explain that gender split?

Andrew Van Dam: Right. I will say that before I explain this, my source on this is none other than Dr. Christopher Warren, who [laughs] happens to be on the line here.

Brigid Bergin: Wow. Live fact-checking. We can have live fact-checking

Andrew Van Dam: My understanding of it is that women tend to have, as they enter childbearing years, more active immune systems. We can see that in things like autoimmune diseases like lupus, where lupus, 90% of the US cases of lupus are in women ages 15 to 45. Now, you can see from an evolutionary perspective why it might be helpful to make sure you are not ill from any of these parasites or other diseases when you are having children and you are raising children. You might pass them on to your children. That seems to know that we don't have the same threats from parasites or whatever lead to women suffering more autoimmune diseases and allergies during that time period.

Brigid Bergin: Dr. Warren, anything you want to add? Did he get it all right as his source?

Christopher Michael Warren: I give him an A on that response. Yes, that was excellent.

Brigid Bergin: That's great. Let's go to Chris in Garden City. Chris, thanks for calling WNYC.

Chris: Thank you for taking my call. I just was wondering my daughter was diagnosed a couple of years back with a nut allergy, cashews, pistachios in specific. She's been developing some other reactions as well, and she also has a little bit of asthma, and we're getting over the asthma. Once the doctor had recommended the possibility of doing, I think it's like some sort of an immunotherapy where they take a little bit of the actual allergen. You guys probably know it better, than I do and how it worked. I just was wondering what is the success rate on something like that?

Christopher Michael Warren: Yes, that's a fabulous question. I think a lot of listeners would probably be familiar with what we call a SCIT or subcutaneous immunotherapy, and that's what's widely referred to as allergy shots. You might be allergic to ragweed, so you go to the allergist and get little shots of ragweed here and there to try to build up your- basically, a desensitization to that allergen.

Oral immunotherapy is what the caller just described. It's basically the same fundamental idea, which is your immune system is overreacting to some substance. In this case, it might be cashews or pistachios or peanuts or what have you. The idea is that you find whatever the smallest possible dose is that you can get that patient to successfully consume without having a reaction, and then slowly, systematically increase that dose over time to the point where-- It depends on the goals of the treatment.

For some folks, it's to build up enough of a response or enough of a tolerance so that they can not have to worry about accidentally being exposed and having a reaction if they were to mistakenly have a bite of a chocolate chip cookie with peanut butter or something, and which otherwise would've put them into anaphylaxis, but now that they've had the OIT, they can just eat and not worry about it.

For other patients, they want to escalate their doses to the point where they can eat freely and eat a whole bag of peanut M&Ms or whatever they want. Obviously, it's more time-consuming, a little more difficult to get people up to tolerating those very high doses.

In terms of the success rate, it's very hard to quote one particular number because up until very recently, most of this OIT was done in private practice allergy, where it's far from a random sample of people, the type of people who are motivated to start the therapy because it is quite intensive. It takes months, typically, and daily modifications to your day in terms of having to limit exercise and things like that.

Also, there are risks of, you're exposing your immune system the things that you know can cause a reaction. Those reactions do occur. The patients who tend to be motivated to stick with it and do end up sticking with it do end up finding that it's effective, but it's a catch-22. I will say, broadly speaking, there is now an FDA-approved therapy for peanut allergy and the same approaches available around the country for all sorts of food allergens, and it does appear to be promising.

Brigid Bergin: I want to go to Robert in Bergen County. Robert has a question that I think probably is at the heart a lot of this is related to, where these allergies begin. Robert, thanks for calling WNYC.

Robert: Hi. Good morning, guys. Thanks for taking my call. Love your show. My question is, are we creating our own allergies by making changes to our diet, like including oat milk and different fat items, I would say? Are we also, by drinking alcohol, does that impact our diet and also help create allergies possibly down the road? When I worked in the city, I had a fantastic lunch buffet at my corporation and I started adding cheese and milk back into my diet. It took like two weeks for my body to learn to reprocess it but then after the two weeks, I was fine.

Brigid Bergin: Robert, thanks for those questions, Andrew, Dr. Warren, any comment on our role in creating some of these intolerances?

Christopher Michael Warren: You want to start, or you want me to, Andrew?

Andrew Van Dam: Oh you know so much more about this than I do that you should obviously start the answer to every single question. If you're ever exhausted, I'll step in, but that's about it.

Christopher Michael Warren: [laughs] I'll fire away, then. Those are really good questions and I do think to the first point about are we backing ourselves into an epidemic of allergy because we have changed our diets so much over the past millennia, decades, years. I would say yes. If you think about the purpose of the immune response that results in food allergy, again, it is a mistaken response, identification of food proteins as something that is harmful to the body when clearly most of these food proteins that the body is reacting to like in cow's milk, like peanut, these are nutritious foods that are otherwise very helpful to the body. Why would it get so confused?

We think this has so much to do with the fact that we have changed our diets so dramatically in terms of the things that we eat now and the things that we feed our kids. If you gave those to somebody out on the Serengeti 10,000 years ago, they would not identify those as food. Not just in terms of a lot of it has to do with the way we process foods. There are things we can do to actually render proteins more allergenic. We really love eating our dry roasted peanuts here in the US whereas other cultures, like in Asia, eat them and some places actually in the southern US are much more likely to boil them.

It turns out when you boil peanuts, you render them a lot less what we call immunogenic or likely to react with the immune system. Whereas if you dry roast them, they're much more likely to induce an immune reaction.

One thing I think is so interesting to think, if you really try to put your head in the perspective of somebody living when our whole human body and apparatus immune system evolved, you were living a hunting and primarily gathering life, where by the time a baby was a couple of years old, they would've almost certainly been exposed to any food that they would then encounter for the rest of their lives as well as most pollens and other environmental allergens that they could find in and around where they're living or in the air.

We've developed this very, very input-sensitive system where the immune system has this critical window early in life when it really learns from the environment. That's why these recommendations that were made about 20 years ago to deliberately not feed kids things like cashews and pistachios and peanuts until they're they're older like two or three years old, we think was completely the wrong way to go. Now evidence is very strong suggesting that that's the case because you're basically missing this window that is so critical to training your immune system what's good, what's bad.

Brigid Bergin: I remember being very struck when I was pregnant, being told to make sure that I continued to eat peanut butter to prevent a peanut allergy. I can say it was to the extent that that is a technique that is science-based and successful, my daughter consumes a tremendous amount of peanut butter with no problems these days, but we have to be very mindful of her classmates, so sun butter, it is.

Christopher Michael Warren: Yes.

Brigid Bergin: Let's go to Angelique in Brooklyn who I think has a question. Angelique, thanks for calling.

Angelique: Hi. Thank you. I have a melon allergy. When I was a kid like my whole life growing up, I ate honeydew and cantaloupe, but I always had like this itchy feeling in my throat, and I just thought it was really fibrous and that everybody got itchy throat when they ate those fruits. Then it was like in my early 20s somebody told me, "Angelique, that means you have an allergy." I was like, "Oh, that's what that means." Since then, I really don't go near them, but if honeydew, cantaloupe, if any melons touch anything I eat, it's like it's gotten worse over the years progressively. Now I can't go near it. If it even touches something, it's contaminated. If it touches any other fruit that I'm not allergic to, I can't go near them.

Christopher Michael Warren: Can I ask you a question, Angelique?

Angelique: Yes, sure.

Christopher Michael Warren: This is Chris. I'm curious. Have you ever been tested for ragweed allergy? Do you have seasonal allergies?

Angelique: I do have seasonal allergies, yes.

Christopher Michael Warren: Yes, so again, I'm not "that kind of doctor." I'm a PhD, not an allergist, but I will say that what you're describing sounds an awful lot like something that we call oral allergy syndrome, or pollen food allergy syndrome. I talked before about how your immune system can get confused about what it's reacting to.

For people who are sensitized or have antibodies that target these ragweed pollens which are ubiquitous in the late summer and fall and also very allergenic, very likely to trigger an immune response, often that immune response becomes generalized to other types of proteins that look a lot like ragweed in terms of their protein structure but obviously aren't. Three of those things are cantaloupe, honeydew, and watermelon.

What the good news is is if that is what you have, it means that it's a fundamentally different type of immune response happening than those in people who have risk of anaphylaxis, like who typically need to carry an EpiPen because they're at risk of very severe reactions.

For oral allergy syndrome like that, the most common symptoms are just restricted to itching, swelling of the lips, the mouth, or throat which I'm sure can be very disconcerting. If it's that local swelling in the throat, it can feel like your throat's closing, but it's different than wheezing or things that are fundamentally happening in the lungs when somebody eats a cashew and has anaphylaxis, so food for thought

Brigid Bergin: Or not, maybe not. Angelique, thanks so much for your call and your question. I want to go to Eddie in Los Angeles who I think is another interesting question. Eddie, thanks for calling WNYC. What's your question?

Eddie: Hi, there. Yes, hi. Just when I hit 50, I suddenly became intolerant to gluten, but it's not like a stomach issue. I get like a psoriasis or a rush kind of [unintelligible 00:23:11] thing on my face, particularly right next to my nose and in my eyebrows, and it's instant. If I have the smallest amount of soy sauce or something like that or definitely anything with flour, even the smallest amount of it causes that to happen.

I was wondering if there's anything I can do to ameliorate it because I love pizza and I love bread and I don't eat any of that stuff any longer. This is all sudden as well. Also, just that interesting, something forever so actually identified that that was the issue that I don't get any symptoms, but really had no idea that it was [unintelligible 00:23:44]. It took me quite a while until some kind of random research clued me in [unintelligible 00:23:49].

Brigid Bergin: Eddie, thanks for that call and question. I think part of that speaks to another caller who I'm going to summarize the question a little bit, which is both how can you explain the onset of an allergy like that, but also why are some allergies so catastrophic and others not as big a deal?

Christopher Michael Warren: In terms of why might somebody develop an allergy, particularly in adulthood or later once they've already learned to tolerate the food and have been successfully tolerating it for most of their life to date, that's still an open question. We do know that fundamentally it's a different question than why do babies get food allergy because they're never developing that tolerance in the first place. Usually, in a baby or an infant or a child, that comes from being sensitized or developing these antibodies to a food protein, and then usually because you're exposed to it in a way that is not encouraging the immune system to develop tolerance.

For example, it's very common for kids who have very dry skin or things like atopic dermatitis or types of eczema, they actually, all that skin inflammation, if the first exposure to an allergenic food-- I know it sounds weird that you would have food exposure through your skin, but there's little dust floating around all over the place. If somebody in this room is eating a bag of peanuts, surely some of that peanut dust is ending up on your skin. If it happens to go in through your inflamed skin, your immune system basically says, "This is probably bad. This is abnormal to have a peanut protein coming in through my inflamed skin so we're going to tag this and make a note of this so next time we run into it no matter where it is we're going to be ready to get it out of here." That's a little different than adults developing allergies.

To go back to Angelique, the previous caller, in things like pollen food allergy or oral allergy syndrome where you have a primary allergy to something in the environment that then gets generalized to other foods, that is a common way that we think allergies develop in adults.

For example, a lot of this rapid or adult-onset shellfish allergy, as Andrew so elegantly described in his post article, we think might have a lot to do with the fact that people are already sensitized to proteins in things in their own house like cockroaches and house dust mites, which as little as we like to think about it, they're all over the place. A lot of people have allergies to them. Their legs and their muscles are actually made of the same thing that shrimp and lobster and crab legs and muscles are made out of. You might start with an allergy to house dust mites, and then your immune system just expands, widens its target to identify some of these other proteins.

In Eddie's case, I can't explain exactly what's going on there. I would encourage him to go get some allergy testing so they can actually better understand the particular mechanism of that gluten allergy. In general, that's some of the thinking behind why we develop these allergies at different ages.

Brigid Bergin: I know that there are lots of hypotheses for why everyone's allergies seem to be going berserk in the past few decades. I understand another one of them is this hygiene hypothesis which has to do with worms. I know you touched on it a little bit, Dr. Warren, but Andrew, can you just briefly explain why scientists think Americans' insides are just too clean?

Andrew Van Dam: Right. Our insides and in some ways our outsides as well, and that is because we do have this immunoglobulin E, the IgE system which probably evolved to target things like these parasites that come in through the skin such as hookworms, roundworms, tapeworms, all these sort of things. It's a pretty powerful system because humanity has been living with these parasites for millennia.

Now this system which was quite effective in dealing with these parasites is all loaded for bear, ready to go out there to take on these threats and there are no hookworms to be found. I don't recommend trying this at home but occasionally, scientists have been so bold as to give themselves hookworms to treat their allergies. In some cases, it has actually been effective. This is not a massive clinical trial. Again, please don't try this, but apparently, yes, hookworms will show your immune system what a real threat looks like and calibrate the response properly.

Brigid Bergin: Wow. Well, I want to bring in Ellen from Manhattan whose grandson took a different approach to dealing with their allergy. Ellen, welcome to WNYC.

Ellen: Thank you. Do I have to turn my radio down?

Brigid Bergin: That would be a good idea.

Ellen: Okay. My grandson is allergic to both cashews and pistachios. That was discovered fortunately not with anaphylaxis, but something approaching. They found a doctor at Mount Sinai who does desensitization. It took about five months. He started with tiny amounts of flour, and built the amount up. At one point, my son made a mistake and gave him something like three cashews, which was far too much for the time of the treatment. Anyway, it absolutely worked. He's able to eat both cashews and pistachios now-

Brigid Bergin: Wonderful.

Ellen: -which is a great savings for them in terms of their own mental health, because they don't worry about him in a classroom. The shrimp allergy is still there, but they figure he can identify shrimp more easily than cashew dust in the room. That's my story.

Brigid Bergin: Ellen, thank you for your call. Thank you. That's some good news in terms of allergy treatment with maybe less controversial or frightening methods.

Andrew, another reason you mentioned in your piece that allergies may be increasing based on the research is Americans potentially overprotecting their kids. Especially, I think this was true in the early aughts when it came to the peanut allergy guidelines, which I mentioned before. Can you tell us the origins of this theory?

Andrew Van Dam: Very simply, and Christopher Michael Warren: may say this is too simple, this is just a way we can think about it, which is, when you're a tiny baby, your body is trying to figure out what's safe, what's not safe. A very simple heuristic it may apply is, well, gees, if it's coming in through the mouth, it's probably food. It's probably good. If it's coming in through the skin, well, it may one of these parasites, hookworms dangerous things that I've evolved over millennia to combat.

In this critical period of the first six months, year of life, your body is making all these decisions on what might be an invader, what might be safe. If it comes in through the mouth, probably safe. It's critical to expose kids, especially if they have a risk factor such as eczema, to these allergens at that time. If we do not expose them orally, if we do not have them eating those things, then their body may make the other decision that those things are probably external, that they're probably invaders.

Brigid Bergin: Wow.

Christopher Michael Warren: I think if you don't mind, I might just append a little bit to that. I think as a very, very broad stroke, that makes sense. I want to add a touch of nuance and I think it's helpful. The human body is this amazing symphony of processes, and then that all this symphony is playing in the orchestra hall of our environment.

It all interacts. I think that if you really want to fundamentally understand why are we having these adverse reactions to foods, you got to think about what's different than when we weren't. What's changed since the time when we weren't having these reactions to foods? One of the biggest changes that Andrew alluded to is with respect to our microbiome.We got something like 30 trillion human cells in our body. We've got more than 30 trillion microbes in our body. We're outnumbered by microbes even in our own bodies.

Part of our immune system responds to and how our immune system is encouraged to do the right things for supporting a healthy body, it's actually has a lot to do with the types of inputs it's getting from the microbes that are in our environment and in our gut. Babies are essentially- the womb, if all goes well, is a sterile environment but as soon as those babies leave, it is a free for all with all these microbes trying to colonize this fresh host.

The point is it matters, and this also returns to the question the other caller had about the effects of alcohol. There are things that we can do to promote a healthy microbiome, both inside and outside and stuff as simple as allowing dogs in your home.

One of the most effective interventions for preventing allergies is just having a dog because that is a connection with our ancestors who used to traverse the indoor-outdoor that it wasn't like the indoors was completely sterile and protected from the outdoors. Those dogs bring a little bit of that helpful outdoors in. I think that's just an important aspect of the hygiene hypothesis. It's not that we've totally cleansed our insides. It's that cleansing our insides then allows these less desirable pathogens and microbes to set up shop. Microbes are going to set up shop.

Brigid Bergin: We are going to have to leave it there for now. My guests have been Andrew Van Dam who writes the weekly Department of Data column for the Washington Post, and Dr. Warren, Assistant Professor of Preventative Medicine and the director of population health at Northwestern University's Center for Food Allergy and Asthma Research. Thank you both so much for coming on today. A lot of great information.

Christopher Michael Warren: Thanks for having us.

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