8 Aug 2023

Why allergies are on the increase around the world

From Afternoons, 3:10 pm on 8 August 2023

Allergies are on the rise worldwide because the human immune system is like a “Windows 95” that can’t be upgraded, a scientist says.

Theresa MacPhail is a medical anthropologist and associate professor of science and technology studies. When her father died from a bee sting, it set her on a path to investigate why allergies are proliferating and what medical science is doing to help.

Her new book is called Allergic: Our Irritated Bodies in a Changing World.

We are becoming more atopic, or more prone to allergies, she tells Jesse Mulligan.

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Photo: 123RF

“A lot of people do have higher levels of IgE (Immunoglobulin E) and their bodies are just primed.

“What has happened over the last couple of hundred years is that our immune systems have lost some of the things that they're used to being around, so some friendly bacteria, and some of the foods that we eat, and we have gained a lot of things that 200 years ago, 300 years ago, 1000 years ago, we would have never have come into contact with.”

We are being exposed to air pollution, chemicals, plastics, antibiotics and our food - things our bodies were not designed for, she says.

“I like to say that our immune systems are like we're running Windows 95, just like a computer, unfortunately, we can't upgrade that system.

“We're trying to do everything in the modern world, but we're running a really old biological system.”

There is a difference an allergy and an intolerance, she says.

“A good example is milk allergy versus lactose intolerance; you're just you're having similar symptoms, but the thing driving that is really different.

“In one case, it's a lack of an enzyme that helps your body break down the milk protein, and in the other your mast cells and the other cells are responding to milk as though it's a threat.”

Pollen has been identified as a problem for hundreds of years, she says, the problem now is there is so much more of it.

“That's related to things like longer growing seasons, especially in the northern hemisphere.

“Climate change; if you're getting warmer areas that can affect your pollen load in the air. So, there's simply a quantity problem, there's more pollen, because of all of that.”

This is the probable reason for adult onset allergies, she says.

“We've been seeing people who maybe a decade ago were not struggling during the pollen season, we've been seeing more and more people develop what's known as adult onset allergies.

“So, they're developing a problem. And it's simply because of the sheer amount in the air.”

Sedentary lifestyles are a contributor too, she says.

Allergic book cover

Allergic book cover Photo: supplied

“There's a link to vitamin D. Vitamin D does impact our immune cells. And so, if you're not outside, you're not getting sunshine. A lot of us have lower levels of vitamin D than we've ever historically had.

“But the other thing is, staying indoors more often has led to, as one allergist said to me, we're sitting on couches that are infested with dust mites, which love moist human environments.

“So, we're indoors and we're getting a lot more exposures with indoor air and dust mites, moulds, and that could be driving some of this change that we're seeing as well.”

Allergies in a warming world

Climate change is making the situation worse in subtle ways, she says.

“The particulate matter from wildfire really irritates the lungs and actually there's a relationship between particulate matter in pollution and wildfire smoke and pollen.

“So, pollen can actually get delivered deeper into the lungs and potentially you can develop asthma or a problem related to frequent exposure to something like wildfire smoke.”

And more wet weather, a consequence of a warming planet, means more mould, she says.

“A study was done in New Orleans after Katrina, even years later, you saw an increase in asthmatic effects related to the mould, the increased mould just from all that leftover dampness everywhere.

“We're seeing that there's not really anywhere that's safe from the effects of climate change on allergies, especially respiratory allergies.”

The alpha-gal allergy

Allergies are becoming more widespread as colder areas warm, she says. One that has emerged in North America is the alpha-gal allergy caused by the lone star tick that had been confined to warmer southern climes but can now be found in Canada.

“Alpha-gal is a sugar molecule that's found in all red meat. Deer have it, cows, pigs. What will happen is when the tick then bites a person, if its last meal was a deer, what it's doing is injecting its saliva, but also a little bit of trace of that alpha-gal.

“And in some people, what that is doing is training the immune system that this is not good.”

The next time they ingest a meat that has alpha-gal, their bodies are responding like someone with a peanut allergy, she says.

“People getting nauseous, people developing all-over body hives, it's quite serious. It can sometimes diminish after a few years, but only if you don't get another tick bite.”

Theresa MacPhail

Theresa MacPhail Photo: SD Studio

Researchers have noticed differences in the microbiomes of people with allergies compared with those without, Dr MacPhail says.

“They've done research here at the University of Chicago, looking at the gut microbiomes of children that have milk allergy, and children that don't.

“And what they found is just a dramatic difference in the makeup of those bacteria.

“The types and the numbers of the bacteria are dramatically different. And what that suggests to researchers is that antibiotics and changes in our diets might be altering our gut microbes to actually prime us to be more allergic.”

Researchers surmise that there's a deep connection between such friendly bacteria that exist in our guts, on our skin and in our nose, and our immune cells, she says.

“Another research study found If you give young children below the age of two repeated doses of antibiotics, then their risk for developing eczema, asthma and food allergy increases dramatically.

“And that would be because obviously, the antibiotics are altering that gut microbiome.”

Consequently, she says, we should be comfortable with less cleanliness, it could help us be less allergic.

“It's really clear that if we simply take a seek and destroy method [to bacteria], we're accidentally destroying things that are helping us. And so, I think that's something we can all do, you can stop using harsh detergents on your dishes, use mild soap, maybe shower every other day, if you're not in a very hot climate, change your sheets less frequently.

“Thinking about giving your body exposure to your natural bacteria that's around and not going too crazy on the antiseptic, hand washing and sprays.”

Early exposure for children is definitely healthy, she says

“Having a dog is good. Studies have shown if you have a dog in the home, when a child is younger, they tend to have less allergies and as adults, and it's probably because they're bringing in a lot of bacteria and licking the kids - it turns out turns out that's ok.”

Thinking on foods has made a 180 degree turn, she says.

“We made a mistake and for years we told parents not to introduce any allergenic foods - soy milk, eggs - until the child was older.”

Early introductions of very small amounts can prevent the immune system from developing a more severe response later, researchers have found.  

“There was a big study in Australia that found the rate of peanut allergy, once they changed the recommendation for peanuts, it went down dramatically.

“So, we're on we're on the right path with that. But basically, that's all we can do, just think about what we're putting on us and what we're putting in us.”