Instant Genius - Allergies, with Theresa MacPhail

Episode Date: July 6, 2023

This week, we’re talking about allergies. Everything from hay-fever to serious nut allergies plague our daily life, but why do we get them? I’m joined by Theresa Macphail, to discuss this topic. She’s the author of the new book Allergic: How our immune system reacts to a changing world. She explains what allergies are, why some are more dangerous than others, and whether there is a possible future where we no longer have to worry about allergies. Learn more about your ad choices. Visit podcastchoices.com/adchoices

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I'm joined by Theresa McPhail to discuss this topic. She's the author of the new book, allergic, how our immune system reacts to a changing world. She explains what allergies are, why some are more dangerous than others, and whether there is a possible future where we no longer have to worry about allergies. It might be quite an obvious question, but I guess allergies is quite a broad term. Could you shed a bit more light on what it is exactly we're talking about here? Absolutely. I think allergy is really kind of a grab bag term. And And that's because it's such an old term and it has such a long history. And most of the allergists that I talk to argue that we really need better terminology,

but we're kind of stuck with allergies. So basically an allergy for lack of a better term is when your immune system kicks on in response to a trigger that is otherwise harmless. So instead of responding to something like a bacteria or a virus, or a parasite, it's responding to something like an oak pollen or a dust mite or a peanut protein. And it's usually driven by a class of antibodies called IGE. But the reason that that's not a great definition is that there are a few allergies that are not IGE mediated. For instance, if you have an allergy to a drug or if you respond like my dad did to a bee sting, then that's actually not

driven by IgE. So it gets really complicated, but I guess if you really want to understand, it's just that the immune system itself is kicking in in some way. And in other things like an intolerance, it doesn't involve your immune system at all. And you mentioned it a little bit there. How long have allergies been around to the best of our knowledge? How far back are we able to trace it? Quite far if you think of things like anaphylaxis. So there's some evidence that, Egyptian Pharaoh died of a wops or a bee sting, actually. But the things that we think of as allergy, so hay fever, food allergy, those are quite new. So the first medical description of hay fever was actually in the UK in 1819. So we think that our modern experience of allergy

is actually dates back to probably the start of the Industrial Revolution, and there are reasons for that. And I don't know about you, but specifically I guess around my allergies, like hay fever and people I know who have asthma, they tend to report that it's just getting worse, that their allergies are getting worse year on year. Is there something I'm imagining or is there actually some science here? No, you're not imagining it is. There is a little bit of a science. So allergies are getting worse in two senses, one in the sense that more people are developing them. And then in the sense of that the people who already had them are reporting that their symptoms are more severe. And for things like respiratory allergies or hay fever, that could be

because we're seeing a lot more pollen in the air and a lot more mold spores in the air. And that's directly related to climate change. Is this more of a environmental thing? Is it genetic? Something else? Or is it just a whole, a whole bunch of things that are coming together to put us in these situations. It's really difficult. It's basically everything. So whenever I would talk to the experts that I interviewed over the last five years, I would try to have them pinpoint the cause of rising allergies. And they all said everything we do. And the reason is, is it is kind of a little bit of this, a little bit of that. So there is a bit of a genetic component. So we do know that allergies tend to run in families, even though you don't inherit the allergy directly.

You inherit the predisposition to allergies. So there's something called atopi. So an atopic individual both has more IGE circulating in their blood naturally, and they also have more receptors on a class of cells called mass cells. And so mass cells are white blood cells that are part of your immune system, and they line all of the parts of your body that are expression. to the world. So they're found in your skin. They're found in your intestinal track, in your nasal track, and even in your bladder and that tract, your urinary tract. So basically they're the first

responders of the immune system. So if they have more receptors for IGE, then it's going to be a little bit easier for people with atopi to be triggered. So we know that that's partially genetic. But we also know that it's not completely genetic because if you look at studies done on identical twins who have obviously the exact same genetic code, we see that quite frequently one of them will develop something like a peanut allergy and the other one won't. And so it also has to do with the environment and how the body is getting triggered. I'm not sure if you've kind of heard the expression about your microbiome and your body connecting to everything and the way that you eat is a way of fixing a lot of different issues. If you don't have, I guess, one of the more severe allergies, is there any kind of connection between your allergies and the way you're eating and the things you put in your body? Absolutely. So that's where our lifestyle comes into play. So they've found researchers at the University of Chicago have been looking at the gut microbiome of young children, infants who have milk allergy versus young infants that do not have a milk allergy. And what they've found is a completely different makeup of that microbiome. So they have different types of bacteria in different portions. So there are, pie chart of what's contained in their gut just look completely different. And so we know that

the gut microbiome is playing a role. And in fact, a lot of researchers theorize that our microbiomes not only in our gut, but in our nasal cavity and on our skin have a huge role to play in the development of the immune system and its regulation. So if you throw off one of the microbiomes, So if you throw off your gut microbiome, say you don't eat enough fiber, so you're starving the bacteria that eat fiber, that consume fiber, and you're giving the bacteria that love fat and sugar a lot of fat and sugar, then you're obviously going to be reshaping your gut microbiome. And that's what we found happens as people move into greater socioeconomic classes. So if you look at places like India and China, you can kind of see them starting to

have problems with food allergy now, and one of the theories behind why is that they're changing how they eat. So they're eating more meat. They're eating less fruit and veg, and they're eating out a lot more because they can afford to. The other two big factors in, I guess, most things, health-related, being sleep and stress, are they linked to allergies as well? Yeah, and it's a little bit chicken than the eggs. So people who have allergies of any kind. So if you have respiratory allergies or eczema or not so much with food allergy, I guess, but the other two, you're not sleeping that well. So there's that connection. Like they are causing interruptions to your sleep, but of course we know that sleep helps regulate the immune system. So it's a little bit of which

thing is driving which thing. So it becomes kind of a self-reinforcing cycle where people aren't getting enough sleep because they're either itchy from eczema or their skin is very sensitive or they're just stuffy and are having trouble breathing at night. So they're waking up constantly. And so that's going to produce a lot less sleep. And so that's going to affect your immune regulation anyway. So it's kind of tricky. And stress, we absolutely know, plays a role. So I had a well-known dermatologist who specializes in eczema. And he said to me that, If you look at the skin, so if you look at someone's skin who is stressed out, so they're working a couple of different jobs or they're worried about paying their bills or they're worried about their

kids, if you look at their skin microbiome, he suggested to me that he can tell how stressed out they are because their skin microbiome will be different and their skin will be more porous, which means that things can seep in and affect that immune system response much more easily. So stress definitely plays a role in our immune system's ability to respond and what it responds to. And I guess it's a bit like you said there, the more stressed you get, the worse your allergies get than you're stressed about your allergies. It's that cycle, isn't it? Yeah, absolutely. In the past actually, so when you look back at what they used to think caused allergy, they actually thought that stress might cause fits of asthma and hay fever.

simply because they often go hand in hand. And again, it's a bit of a cycle there. So let's say someone starts coming out in hives or having these random reactions to something, but they just don't know what it is. They can't pinpoint it. What's the steps? Where do you go to identify your allergies?

I think most people will probably go to their regular physician, which is maybe not the best solution, which I'll talk about in a second. But when you do go and you describe symptoms, you'll probably get a skin test. So they'll do a skin prick test, which is just delivering a very trace amount of an allergen underneath the skin to see if it produces a histamine response.

So in essence, they're checking to see if your mass cells will respond to this thing. And it usually takes about 20 to 30 minutes to see reactions. However, that is only testing your sensitivity, which means are you prone to maybe responding to that thing in real life? So if you think about it, scratching your arm with an oak pollen isn't the same as inhaling an oak pollen. So you could actually respond on your arm and have a sensitivity to oak pollen. And that might indicate that that's what you're reacting to in the air, but not necessarily. So there's about a 50% false

positive rate on positive skin test for allergies. And I, I think a lot of people don't understand why, and it's really the difference between the sensitivity and the full-blown allergy. So you could have the sensitivity, but then see the thing in real life and your immune system is perfectly happy with that thing being in the area. It's peak pollination season, and my business is scaling fast. To keep the nectar flowing, I need a phone plan with top priority data speed. That's why I chose GoogleFi wireless. My connections stay strong even when the hive was buzzing. Plus, unlimited plans started $35 a month.

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It does make me think a little bit and throwing in my very personal, random anecdotes to it. But years ago in, I guess an effort to sort my expert, I went and had one of those kind of tests done. and I was given this an incredibly long list of different foods and things that could be causing it and was told, you know, you have these minor intolerances to potatoes and milk and all these different things like that. Should we be treating, I guess, the more serious issues and the minor intolerance is the same? Or is it a little bit crazy to try and monitor every little thing that affects you?

It's really difficult. So when I said you're usually going to your jewellery. The reason that you should probably try to see an allergist is they're better at interpreting those tests. So if the skin test isn't really giving them a lot of information, you can also do a blood test where you add antigen into a little bit of the patient's blood and you see if the IgE cells respond to that thing. That's a lot more accurate. That's the only one that they use to test for food allergies. Skin is traditionally thought of as a really bad predictor for a food allergy. So you tend to look at blood test results and then an allergist will ask people to keep track of their symptoms in relation to what they're eating or they'll do the gold standard is the double blind food challenge. So you'll go into the office, you'll be given a very small amount of food allergen and then you'll wait 45 minutes and then they'll test your blood and see if you're having any reaction physically. And that is considered the gold standard for food allergy. One of the really dangerous things, so say you get the skin panel and you think you're sensitive to peanuts, but you're having really no issue like your body is actually fine, digesting the peanuts.

What can happen is if you avoid an allergen, one of the major allergens, and you do not eat it for a while, you are lowering your immune system's tolerance. So you might have been tolerating that thing just fine, but then if you subtract it from your system and you're, immune system doesn't regularly run into it and it has a predisposition to maybe think that that thing is not okay, then you are accidentally causing the problem you thought you had. We've touched a little bit on the, I guess the issue of allergies to peanuts. And I think that's the best known one in terms of a very serious life-threatening issue. Is there a reason that some allergies are very, you you know, minor and some have these incredibly high stakes behind them?

Well, it's a really interesting question, and we really don't know that much about why one person will react the way they react, and another person will react very differently. So allergies are incredibly unique, partially because immune cells have different pathways that they can take. They're called biological pathways. And there's different mechanisms that they can turn on and off in relationship to something that they encounter. And if you think about it like a pin code, so your pin code is four digits, but you have 10 digits to plug in those numbers. So if you forget your pin code, that's literally thousands of possibilities. And your cell does the same thing. So it has a few different choices, but the order of those choices and what it does,

you can potentially have thousands of different responses in the whole body. because each cell is kind of triggering a different thing. So that's why I can have a shellfish allergy, and you might have a shellfish allergy, but mine just causes a little bit of hives, and yours sends you to the ER. So it's really dependent on what your body is chosen to do. And again, that can be also influenced by what's going on in your life.

So hormones, both stressed hormones and sex hormones can affect this. Other things can affect a time of day. can affect it. So maybe you're fine in the morning with oak pollen, but by the evening, your body has had it and your response is a lot stronger. And we really don't understand exactly what's going on with the cells when they're making those decisions in the first place. So obviously that at its current stage, a lot of these are treatable in the sense that you can deal with a allergic reaction, but they're not curable. Is there a future where that changes, where we could, you know, eradicate our allergies and just be done with

them? God, wouldn't that be nice? Wouldn't it? I mean, the problem with allergies is that to cure them in the sense that we usually think about curing something would mean turning off the immune system, which obviously we cannot do because then we'd be back to the days where you're dying from pneumonia or, you know, we can't do that, which is why steroids aren't such a great idea on the long term. Steroids work wonders for a lot of people who are in allergic responses because it does exactly that. It kind of times down the immune system full stop and it stops the allergic reaction, but it also stops every other function of the immune system like fighting off bacteria, which is not a great solution. So the solution to allergies is really trying to,

to get to that point where the first cell is making that decision. So say your T-cell comes into contact with a peanut protein, it can either decide that that thing is okay to become a part of you and thereby tolerate it and just leave it alone, or it can decide, hey, I don't like the looks of this thing. Remember it. Take a molecular snapshot, if you will, of this thing, and then ask the B cells next to it to produce the IGE antibodies against that thing. So if we can get in the middle of that and kind of train the immune system to tolerate something, so that would either mean that we wipe the memory of T cells. So there's a lot of research going on to see, can you erase the memories of T cells?

So the T cells that have decided that the peanut protein is bad, can we blank their memory? and get them to forget that they don't like peanut and then get them slowly to tolerate peanut, or can we somehow figure out how a T-cell thinks, for lack of a better word, like how they're making those decisions, and then do something to prime them to not make the choice we don't want them to make in response to a protein? So they're doing really interesting experiments on things like nanoparticles or even using the mRNA technology that was just used in the COVID vaccine, they think that maybe there's a way that we could deliver something like a peanut protein to the lymph nodes or other areas that are

producing white blood cells and kind of get everyone on board inside your body to be like, oh, this is actually fine. This is supposed to be here. It's not causing an issue. That would be a cure because you're preventing the response in the first place, not just trying to deal with the symptoms once the problem has developed. So it's something that I always found quite interesting is that I live in a city and my allergies are, for whatever reason, always better there than when I go to see my parents in a much smaller area in a small town. But I would assume that air pollution would play a big role in your allergies.

But is it that that's not so much an issue and does the place you live affect your allergies hugely? Both. So we do know that unfortunately air pollution does interact with pollen in ways that produce more allergic disease. So researchers at the Cincinnati Children's Hospital, which is one of the premier children's hospitals here in the U.S., Cincinnati is in a river valley. So they have quite stagnant air depending on their weather patterns. And they also have three major interstate highways running through their city. So you're talking to talking about a lot of diesel truck engines, up to, you know, 70,000 a day on just one of the roads. So researchers there wanted to understand the relationship between these diesel particulates, which are really particularly nasty air pollution particles. They're tiny, tiny, tiny. So they tend to be less than 2.5 microns. And just so people understand what we're talking about, five microns is the diameter of a red blood cell. So we're talking about things. things that are smaller than a red blood cell in the air. And you can't see them. So if those are high,

so if you see a high particulate matter count of 2.5, you're not necessarily going to be able to look out your window and see them. So they wanted to understand, are these things producing more allergic disease like asthma? And they recruited parents who had just had a child. So the study has been running for, I think, 22, 23 years now. And they picked people randomly, and then they placed them in relationship to these major highways and other sources of pollution. What they found was the closer a child was to a source of pollution, so either a factory, a bus depot, one of these highways, their risk for developing asthma went through the roof. So there's basically a one-to-one. And the reason is these particles are so small that they can be delivered deeper into your lungs,

and they can actually attach to pollen. So if you like, it's like pollen being able to grab a cab and get delivered deeper into the lungs. So the combination of air pollution and pollen is particularly bad. So you're going to get more allergic disease in places with higher air pollution. So I think a good place to end. In your book, you take a really comprehensive look at the past, the present, the future of allergens all the way through. Is this a field that we've cracked? Or is this more like the ocean where we've barely scraped the surface? We've barely scraped the surface. I mean, we really started thinking about the immune system around the turn of the last century. So we're looking at maybe 170. years, 120 years. And allergic disease has gotten short shrift in funding. So it's gotten less funding until very recently. So if you look at the National Institute of Health Budget here in the

U.S., they spend about $6 million a year trying to understand hay fever, which affects 30% of the global population. Meanwhile, they're spending $6 billion to understand aging. Now, I'm not suggesting we not understand aging. Like, obviously, we need to understand aging. But I mean, you just see the priority difference there, despite the fact that so many of us are suffering. So the funding really hasn't caught up to the amount of disease that we're seeing, the sheer numbers of people with some form of allergic disease. So I'm hoping that what will happen in the future is that we fund more basic science.

So really we need to stop looking for treatments and we need to start understanding why those T cells are thinking the way that they think about the things in our bodies. And we really, really have at this point in time, zero understanding of that, of why the cells in our bodies are making the decisions that they make, we also do not understand our microbiomes at all. That very much is like

a deep sea kind of thing. In effect, we have an ocean inside of us and on us that we know nothing about. I heard someone who works on the microbiome say it this way the other day that it's like 10 years ago we discovered a whole new organ that we didn't even know we had. And so we don't even know the different types of bacteria. So if you do a genetic sampling of gut microbiased, There are gene segments that we don't even recognize. We don't know what they are. So until we understand what's in us and on us and how that's interacting with our immune cells, I think we're going to be behind the eight ball on this.

Thank you for listening to this episode of Instant Genius. That was Theresa McFell talking about allergies. The Instant Genius podcast is brought to you by the team behind BBC Science, Science Focus magazine, which you can find on sale now in supermarkets and newsagents, as well as on your preferred app store. Alternatively, you can come find us online at sciencefocus.com. This podcast is sponsored by Name, Audio and Focal. The texture and emotional depth of music can be lost through digital sources or poor signal. Name audio believes you can have digital precision with analog warmth.

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