Food allergies appear to be increasing globally, but as scientific understanding improves, some experts believe we may one day be able to eliminate them altogether. Ian Sample speaks to Dr Kari Nadeau, an allergy specialist at Harvard School of Public Health and author of the book The End of Food Allergy, to discuss why food allergies are on the rise and what we can do to prevent – and possibly even cure – them. Help support our independent journalism at theguardian.com/sciencepod

They can be inconvenient, worrying, and in rare cases, even fatal.

And they seem to be on the rise, with some studies suggesting that rates of peanut allergy among children in western countries have doubled in a decade.

But we also understand more than ever about what causes and what might prevent allergies.

Some experts believe that 1 day we may be able to eradicate them altogether.

So what's behind the rise in food allergy?

I'm the Guardian's Science Editor, Ian Sample, and this is Science Weekly.

Kari Nadeau, you're chair of the Department of Environmental Health at Harvard School of Public Health, and you practice allergy, asthma, and immunology in children and adults.

You're also the author of the book, the end of food allergy.

First of all, can we distinguish between a food allergy and a food sensitivity?

So a food allergy is a disease in which when you bite into a food within 2 hours, you can get hives or stomach ache or breathing issues.

And the reason behind that allergy, you have a preformed molecule in your body called IgE that is like the match that lights the fire that within 2 hours after eating a food no matter what dose really you can actually have a reaction.

What's causing that to happen is a protein And these proteins are typically in items like shrimp or milk or nuts or seeds.

And at any point in life, if you eat that food, you will have a reaction.

With a food sensitivity, that's different.

When you eat a food, you could have bloating or you can have a headache or you can have a stomachache.

That can happen at any point in time, not within 2 hours.

And in addition, a food sensitivity can vary over someone's lifetime and it's not caused by a specific molecule called IgE in your body.

We think that in certain countries, peanut is definitely more frequently the food allergen in that population.

For example, in Australia, the UK, as well as the States.

However, in other countries like Italy or like Norway, their allergies are to hazelnut or walnuts.

And then in other countries, their major allergen is milk, for example, in China or in Japan.

Why is there this country to country to country difference?

My colleagues in King's College London and Guy's St.

Thomas's actually found that when they dusted up and when they vacuumed up homes, they could find the peanut dust in the air.

And the more peanut dust in the air and the more skin breakdown there was in that family, the increased risk of peanut was in that family.

So we think that to some degree, the environment and the exposures are inducing peanut allergies in those countries.

However, in other countries, they have different things on the breakfast table, for example, and so their dust might have hazelnut in it.

Do we know what proportion of people suffer from allergies like this and perhaps it changes country to country?

So for example, in the States, it's about 1 in 12 children in every classroom have a doctor's definition of food allergy.

In adults, we think that approximately 1 in 30, 1 in 40 adults have a doctor's diagnosis of food allergies.

1 is that it's less likely now that children will outgrow their food allergies, so more adults have them.

But in addition, more adults compared to, let's say 10 years ago, are acquiring new food allergies for which they did not have before.

lot of information out there talking about how rates of allergies are increasing, but there is some debate in the community, isn't there?

I mean, in some countries, the rates of deaths from anaphylaxis have been pretty stable since the 80s, despite hospitalization rates increasing.

And I know Some doctors have used that to say, well, actually maybe we're just increasingly aware of allergies.

We're diagnosing them more and stuff like that.

Do you think there is a genuine rise in the population of allergic diseases?

Or do you think this is us being just better able to pick them up?

Anneke Vandenbroek For different countries, we might have different prevalence and incidence data, because they might have qualified and gotten data about deaths in a different way than another country.

Not everyone uses the same definition when you go to the emergency room.

They just qualify it as a death due to wheezing.

It might not actually come out as a death due to wheezing due to a peanut injection, for example.

So you really have to unpack the data when you do these types of studies.

So that's 1 reason why there might be variability in terms of diagnosis, but also in terms of severe reactions.

The other aspect is, yes, there is a rise in incidence and prevalence.

In some countries, for example, sesame is doubling every 2 years in the rate of rise for its food allergy in certain countries.

Walnut, for example, and tree nuts are doubling every 10 years in certain countries.

People always ask, well, is it just because you're getting better at diagnostics?

Actually, unfortunately, I can tell you know, that our diagnostics skin testing have been around for hundreds of years.

So I wish I could say we're getting better at diagnostics, but we're really not.

So if we accept then that the rates are genuinely going up, I wonder if you could break down for us the kinds of theories scientists have for what's causing this.

Right now the mantra is through the skin allergies begin, through the diet allergies can stay quiet.

And the reason why we think that is, is because as we look at the skin, it's the entry point which our body uses to protect against foreigners.

Now it's important to know that skin dryness is increasing around the world.

That's due to a lot of areas of the environment.

We need to worry about detergents, we need to worry about preservatives as well as different synthetics on clothing.

So that dryness leads to cracking, that cracking leads to areas of the skin which when exposed to normal dust or normal air that can lead to increases in allergies in general.

So that's the first possible causation is through the skin.

Unfortunately, many years ago, there was a thought that we should only be feeding our babies 1 thing at a time or not feeding them a lot of diversity of proteins initially when they're born.

Now it's been shown across Europe, the UK, across many different countries that those countries that had been not listening to the guidelines from the year 2000 and actually just staying with their native culture and feeding their babies what was on the table with the other family members.

They were the ones that had the least food allergies in their cultures.

So we know that diversity of diet, making sure that children are eating lots of different proteins by the time they're 4 to 6 months of age is actually helpful.

DePriest The next is what I'm going to call dirt.

Having good microbiome, having access to animals, for example, there's been a lot of farm studies showing that if you live on a farm and you're exposed to a lot of animals, you actually have less likelihood of getting allergies and food allergy.

What's thought is that by making sure that we have good microbiota in our gut, having good complement of animals and dirt and dogs, that that can actually help protect us against food allergies and allergies.

And so a lot of people are doing work in that area.

Presumably, our own human genetics has some role in this as well.

But on top of the genes, there is this other field called epigenetics that we should talk about.

Because as you get exposed to the environment, you can actually change your genes and that change of the genes can be inherited.

And so for example, if you eat a lot of really good foods and you have a great diet and you exercise, that can actually help your genes stay more protective by changing those genes and that can be inherited to your children.

But on the flip side, if you smoke or you have a lot of preservatives in your diet or you don't have a lot of exercise or you're obese, those behaviors can change your genes and then they are malfunctioning changes in genes that can be inherited by your children as well.

So this concept of epigenetics is another layer on top of your already given genes in your body that we need to think about carefully.

And I was wondering if any of the changes we're seeing in the climate are a factor at all.

I don't know if that might have any impact on the types of allergens we're exposed to as so.

So we see that the rise in CO2 will increase plant growth.

I wish that it would be the better plants like broccoli and spinach but unfortunately it actually is more healthy unfortunately for plants like grasses and ragweed.

So CO2 increases make pollen producing plants proliferate.

And so now we're seeing across the planet increases in pollen plants increasing in those plants to areas that they shouldn't be in, for example, like in Norway or near the Arctic Circle.

So more and more people are getting new aeroallergies where they didn't before.

So climate change is definitely affecting asthma and allergic rhinitis.

In addition, climate is affecting our skin like wildfire smoke due to global warming.

That smoke itself irritates the skin, causes breakdown and that's where we're seeing an increased chance of food allergy.

The other aspect to our world in the facing climate are extreme conditions that lead to vector-borne diseases.

And those diseases, even though they're not directly associated with allergies, they can induce allergies and they can induce a switch in the immune system over time.

And then finally, there's going to be water insecurity.

And when there's water insecurity, water will be more concentrated with certain toxins or detergents that have to be used to clean the water.

And those detergents are not healthy for our gut.

And because of that, we expect that there'll be much more gut inflammation and potentially allergies.

If a child does have a serious food allergy, It can obviously be incredibly scary and stressful.

Your research has looked at oral immunotherapy for food allergies.

So what we do is whether or not you have a single or a multiple food allergy, we give you those exact foods that you are allergic to and we slowly over time increase that dose.

And it's just like when you go to the gym and you lift weights, You start with a low weight and then you climb up over time, but you don't do the heavy weights all at once.

So what happens is while you're slowly advancing and increasing these small amounts of food proteins, and they are literally in small amounts of dry food proteins that you weigh very carefully.

But over time, you're building your immune muscle.

Within about 1 to 2 years, you can reach levels that at least protect you against an accidental ingestion of that food.

So this has been going on for at least a century.

It was originally done in London by a physician that was published in Lancet with a little boy that had egg allergy.

And then this type of therapy became used throughout Europe, Published at first with colleagues in Spain with milk.

Then it became used in the States for peanut, for example.

And it still needs to be approved by the FDA and the EMBA and the MHRA for other foods other than peanut.

But at least for now we do have an approved product for oral immunotherapy now for peanut.

And can patients be cured by that kind of exposure?

I do believe that some people have completely lost their food allergies through this method.

I have some of my own patients that I've seen completely lose the food allergy by using immunotherapy and their skin tests go negative, their blood tests go negative, and they can eat AdLib and they can eat however much of that food that they want.

But there seems to be 3 different categories of people where when they take the immunotherapy, they just have too many side effects and they get worried and so they just stop.

Then there's another category where they might not be cured, but they need to take the food every day for the rest of their life, like a vitamin.

And they are able to eat the food but they need to eat it every day to stay tolerized.

And then there's a third group that actually is cured-cured and they actually completely lose the food allergy by this therapy.

And how widely available is that treatment now?

You can get this therapy in certain areas of the country but you might have to pay out of pocket which hopefully is not the case in the future so that this is approved globally and that it can be democratised to be helpful to everyone.

Your book is called The End of Food Allergy.

Do you really think that's something we can achieve that's within our reach?

Now that I've seen some patients in which their food allergy has been ended.

I want to understand that better and also make sure that people know that that can be reached and it might not be reached for everyone right now at this current time but that we should have it as a goal and most importantly prevent it from happening in the first place.

So I am excited about being able to deliver on that hope and promise but we need to do it together as scientists, as researchers, as physicians, as parents and as citizens.

Well best of luck with that Kari and huge thanks for coming on.

Her book, Ending Food Allergy, is available now.

And the executive producer was Ellie Burey.


Speaker 0: This is The Guardian. Food allergies. They can be inconvenient, worrying, and in rare cases, even fatal. And they seem to be on the rise, with some studies suggesting that rates of peanut allergy among children in western countries have doubled in a decade. But we also understand more than ever about what causes and what might prevent allergies.

Some experts believe that 1 day we may be able to eradicate them altogether. So what's behind the rise in food allergy? How can we protect ourselves? What would a cure look like? I'm the Guardian's Science Editor, Ian Sample, and this is Science Weekly.

Dr. Kari Nadeau, you're chair of the Department of Environmental Health at Harvard School of Public Health, and you practice allergy, asthma, and immunology in children and adults. You're also the author of the book, the end of food allergy. First of all, can we distinguish between a food allergy and a food sensitivity? What's the difference there?

Speaker 1: So a food allergy is a disease in which when you bite into a food within 2 hours, you can get hives or stomach ache or breathing issues. And the reason behind that allergy, you have a preformed molecule in your body called IgE that is like the match that lights the fire that within 2 hours after eating a food no matter what dose really you can actually have a reaction. What's causing that to happen is a protein And these proteins are typically in items like shrimp or milk or nuts or seeds. And at any point in life, if you eat that food, you will have a reaction. With a food sensitivity, that's different.

When you eat a food, you could have bloating or you can have a headache or you can have a stomachache. That can happen at any point in time, not within 2 hours. And in addition, a food sensitivity can vary over someone's lifetime and it's not caused by a specific molecule called IgE in your body.

Speaker 0: What is going on with peanuts? Why are they such common allergy?

Speaker 1: We think that in certain countries, peanut is definitely more frequently the food allergen in that population. For example, in Australia, the UK, as well as the States. However, in other countries like Italy or like Norway, their allergies are to hazelnut or walnuts. And then in other countries, their major allergen is milk, for example, in China or in Japan. Why is there this country to country to country difference?

My colleagues in King's College London and Guy's St. Thomas's actually found that when they dusted up and when they vacuumed up homes, they could find the peanut dust in the air. And the more peanut dust in the air and the more skin breakdown there was in that family, the increased risk of peanut was in that family. So we think that to some degree, the environment and the exposures are inducing peanut allergies in those countries. However, in other countries, they have different things on the breakfast table, for example, and so their dust might have hazelnut in it.

Speaker 0: Do we know what proportion of people suffer from allergies like this and perhaps it changes country to country?

Speaker 1: So for example, in the States, it's about 1 in 12 children in every classroom have a doctor's definition of food allergy. In adults, we think that approximately 1 in 30, 1 in 40 adults have a doctor's diagnosis of food allergies. And that's probably due to 2 things. 1 is that it's less likely now that children will outgrow their food allergies, so more adults have them. But in addition, more adults compared to, let's say 10 years ago, are acquiring new food allergies for which they did not have before.

There's a

Speaker 0: lot of information out there talking about how rates of allergies are increasing, but there is some debate in the community, isn't there? I mean, in some countries, the rates of deaths from anaphylaxis have been pretty stable since the 80s, despite hospitalization rates increasing. And I know Some doctors have used that to say, well, actually maybe we're just increasingly aware of allergies. We're diagnosing them more and stuff like that. Where are you on this?

Do you think there is a genuine rise in the population of allergic diseases? Or do you think this is us being just better able to pick them up?

Speaker 1: Dr. Anneke Vandenbroek For different countries, we might have different prevalence and incidence data, because they might have qualified and gotten data about deaths in a different way than another country. Not everyone uses the same definition when you go to the emergency room. They just qualify it as a death due to wheezing. It might not actually come out as a death due to wheezing due to a peanut injection, for example.

So you really have to unpack the data when you do these types of studies. So that's 1 reason why there might be variability in terms of diagnosis, but also in terms of severe reactions. The other aspect is, yes, there is a rise in incidence and prevalence. In some countries, for example, sesame is doubling every 2 years in the rate of rise for its food allergy in certain countries. Walnut, for example, and tree nuts are doubling every 10 years in certain countries.

So these are real data. People always ask, well, is it just because you're getting better at diagnostics? Actually, unfortunately, I can tell you know, that our diagnostics skin testing have been around for hundreds of years. They're rather draconian. So I wish I could say we're getting better at diagnostics, but we're really not.

Speaker 0: So if we accept then that the rates are genuinely going up, I wonder if you could break down for us the kinds of theories scientists have for what's causing this.

Speaker 1: Right now the mantra is through the skin allergies begin, through the diet allergies can stay quiet. And the reason why we think that is, is because as we look at the skin, it's the entry point which our body uses to protect against foreigners. Now it's important to know that skin dryness is increasing around the world. That's due to a lot of areas of the environment. We need to worry about detergents, we need to worry about preservatives as well as different synthetics on clothing.

So that dryness leads to cracking, that cracking leads to areas of the skin which when exposed to normal dust or normal air that can lead to increases in allergies in general. So that's the first possible causation is through the skin. The other is through our diet. Unfortunately, many years ago, there was a thought that we should only be feeding our babies 1 thing at a time or not feeding them a lot of diversity of proteins initially when they're born. Now it's been reversed.

Now it's been shown across Europe, the UK, across many different countries that those countries that had been not listening to the guidelines from the year 2000 and actually just staying with their native culture and feeding their babies what was on the table with the other family members. They were the ones that had the least food allergies in their cultures. So we know that diversity of diet, making sure that children are eating lots of different proteins by the time they're 4 to 6 months of age is actually helpful. Dr. DePriest The next is what I'm going to call dirt.

Having good microbiome, having access to animals, for example, there's been a lot of farm studies showing that if you live on a farm and you're exposed to a lot of animals, you actually have less likelihood of getting allergies and food allergy. What's thought is that by making sure that we have good microbiota in our gut, having good complement of animals and dirt and dogs, that that can actually help protect us against food allergies and allergies. And so a lot of people are doing work in that area.

Speaker 0: Presumably, our own human genetics has some role in this as well. What's been teased out about that?

Speaker 1: Genetics probably play a role about

Speaker 0: 30%

Speaker 1: of the time, the environment about 70%. But on top of the genes, there is this other field called epigenetics that we should talk about. Because as you get exposed to the environment, you can actually change your genes and that change of the genes can be inherited. And so for example, if you eat a lot of really good foods and you have a great diet and you exercise, that can actually help your genes stay more protective by changing those genes and that can be inherited to your children. But on the flip side, if you smoke or you have a lot of preservatives in your diet or you don't have a lot of exercise or you're obese, those behaviors can change your genes and then they are malfunctioning changes in genes that can be inherited by your children as well.

So this concept of epigenetics is another layer on top of your already given genes in your body that we need to think about carefully.

Speaker 0: And I was wondering if any of the changes we're seeing in the climate are a factor at all. I don't know if that might have any impact on the types of allergens we're exposed to as so.

Speaker 1: So we see that the rise in CO2 will increase plant growth. I wish that it would be the better plants like broccoli and spinach but unfortunately it actually is more healthy unfortunately for plants like grasses and ragweed. So CO2 increases make pollen producing plants proliferate. And so now we're seeing across the planet increases in pollen plants increasing in those plants to areas that they shouldn't be in, for example, like in Norway or near the Arctic Circle. So more and more people are getting new aeroallergies where they didn't before.

So climate change is definitely affecting asthma and allergic rhinitis. In addition, climate is affecting our skin like wildfire smoke due to global warming. That smoke itself irritates the skin, causes breakdown and that's where we're seeing an increased chance of food allergy. The other aspect to our world in the facing climate are extreme conditions that lead to vector-borne diseases. And those diseases, even though they're not directly associated with allergies, they can induce allergies and they can induce a switch in the immune system over time.

And then finally, there's going to be water insecurity. And when there's water insecurity, water will be more concentrated with certain toxins or detergents that have to be used to clean the water. And those detergents are not healthy for our gut. And because of that, we expect that there'll be much more gut inflammation and potentially allergies.

Speaker 0: If a child does have a serious food allergy, It can obviously be incredibly scary and stressful. Your research has looked at oral immunotherapy for food allergies. What are those and how do they work?

Speaker 1: So what we do is whether or not you have a single or a multiple food allergy, we give you those exact foods that you are allergic to and we slowly over time increase that dose. And it's just like when you go to the gym and you lift weights, You start with a low weight and then you climb up over time, but you don't do the heavy weights all at once. So what happens is while you're slowly advancing and increasing these small amounts of food proteins, and they are literally in small amounts of dry food proteins that you weigh very carefully. You do not do this at home. But over time, you're building your immune muscle.

Within about 1 to 2 years, you can reach levels that at least protect you against an accidental ingestion of that food. So this has been going on for at least a century. It was originally done in London by a physician that was published in Lancet with a little boy that had egg allergy. And then this type of therapy became used throughout Europe, Published at first with colleagues in Spain with milk. Then it became used in the States for peanut, for example.

And it still needs to be approved by the FDA and the EMBA and the MHRA for other foods other than peanut. But at least for now we do have an approved product for oral immunotherapy now for peanut.

Speaker 0: And can patients be cured by that kind of exposure?

Speaker 1: I do believe that some people have completely lost their food allergies through this method. I have some of my own patients that I've seen completely lose the food allergy by using immunotherapy and their skin tests go negative, their blood tests go negative, and they can eat AdLib and they can eat however much of that food that they want. But there seems to be 3 different categories of people where when they take the immunotherapy, they just have too many side effects and they get worried and so they just stop. Then there's another category where they might not be cured, but they need to take the food every day for the rest of their life, like a vitamin. And they are able to eat the food but they need to eat it every day to stay tolerized.

And then there's a third group that actually is cured-cured and they actually completely lose the food allergy by this therapy.

Speaker 0: And how widely available is that treatment now?

Speaker 1: You can get this therapy in certain areas of the country but you might have to pay out of pocket which hopefully is not the case in the future so that this is approved globally and that it can be democratised to be helpful to everyone.

Speaker 0: Your book is called The End of Food Allergy. Do you really think that's something we can achieve that's within our reach?

Speaker 1: Yes, I do. Now that I've seen some patients in which their food allergy has been ended. I want to understand that better and also make sure that people know that that can be reached and it might not be reached for everyone right now at this current time but that we should have it as a goal and most importantly prevent it from happening in the first place. So I am excited about being able to deliver on that hope and promise but we need to do it together as scientists, as researchers, as physicians, as parents and as citizens.

Speaker 0: Well best of luck with that Kari and huge thanks for coming on.

Speaker 1: Thank you, Have a good day.

Speaker 0: Thanks again to Dr. Kari Nadeau. Her book, Ending Food Allergy, is available now. This episode was produced by Silas Gray. The sound design was by Tony Onuchukwu.

And the executive producer was Ellie Burey. We'll be back on Tuesday, see you then! This is the Guardian.

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Why are food allergies on the rise and is a cure on the horizon?