A Clear-Eyed Look at the Red-Eye Culprit

“Don't just rely on the textbook definition of when the pollen seasons are. You need to have reliable data to know when the pollen seasons are starting, when they're ending, and when they're peaking.”  Dawn Jurgens

Allergy season may be winding down, but for allergists, the work never really stops. This is the moment between ragweed and winter — a brief respite before the cycle begins again. On this episode, Dr. Mariam Hanna is joined by Dawn Jurgens, Director of Operations and Quality Management at Aerobiology Research Laboratories. She breaks down the science behind pollen and spore counts, why forecasts matter, and how shifting seasons are changing the game for patients and clinicians alike.

• Timothy grass is the most common and potent trigger globally, while birch remains the most clinically relevant pollen in Canada. Pine releases large amounts of pollen but isn’t highly allergenic.
  
  
• Pollution and thunderstorms can make pollen more potent by breaking it apart and exposing allergenic epitopes, intensifying symptoms.
  
  
• Cross-reactivity stems from conserved epitopes, meaning patients sensitized to one pollen may react to related species — or even certain foods.
  
  
• Mold spores, especially Alternaria, Cladosporium, and Basidiospores, can mimic ragweed season and are major fall culprits.
  
  
• Canada’s pollen seasons are starting earlier than they did 30 years ago, though the fall season hasn’t yet extended.
  
  
• Simple strategies — like showering before bed, keeping windows closed, using filters, brushing pets outside, and checking reliable forecasts — can meaningfully reduce exposure.

Pollen season may be taking a break, but planning for the next wave starts now.

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The Allergist is produced for CSACI by PodCraft Productions

Transcript

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Dr. Mariam Hanna Hello, I'm Dr. Mariam Hanna, and this is The Allergist, a show that separates myth from medicine, deciphering allergies and understanding the immune system. For centuries, humanity has looked to the skies, not to chart starships among the stars, but to search for signs of what tomorrow might bring. From ancient farmers scanning the clouds, to sailors invoking the favour of storm gods and wind spirits, our survival has always been bound to the weather above. Where once the gods of thunder and rain held sway, today, satellites, radars and forecasts carry their mantle. And now, a new frontier in prediction has emerged, not just storms or sunshine, but pollen. Modern science lets us glimpse when invisible clouds of allergen may rise, shaping our health and our days. This is the story of how looking to the sky has always guided us, and how pollen forecasts have become the latest chapter in that timeless search. I'm just kidding. Anyways, today, I really, really, really wanted us to talk about pollen forecasts and pollens because they have become integral in the allergist's life. As allergists and immunologists, we train our immune systems to be less allergic to stuff. And the way we do that is knowing which ones are the culprit for symptoms with our patients and starting something called immunotherapy, which has become near and dear to all our practices. Today, it's my pleasure to introduce you to an official aerobiologist. We all pretend that we are part aerobiologists in allergy and immunology, but we don't have the full degree, which is why Dawn Jurgens is joining us today. She holds a master's degree in biochemistry, microbiology and immunology. She is the Director of Operations and Quality Management at Aerobiology Research Laboratories. She leads a team of talented and dedicated technicians in the collection and analysis of pollen and spores from across Canada. She's also going to talk to us about the rest of the world, but her knowledge and expertise is focused in Canada. She's heavily involved in research projects involving pollen and spore data with a variety of pharmaceutical companies and academic researchers. Today, it's an absolute pleasure to have you with us. Dawn Jurgens, welcome to the podcast. Dawn Jurgens Thanks for having me. Dr. Mariam Hanna So, Dawn, I thought a great interesting fact to start with would be to understand what's the most common seasonal allergy trigger, not just here in Canada, but globally that we see. Dawn Jurgens So basically, pollen from wind-pollinated plants, trees, grasses and weeds are the most common. What specifically is the most common is grass. Timothy grass is a very potent allergen and it can grow in pretty much any temperate climate. So anywhere around the world, North America, Europe, Asia, and then through South America and Australia as well. It doesn't really grow very much in dry, arid climates. So Africa does not have a lot of grass pollen to worry about. The major allergen to worry about in Africa, for example, is fungal spores. Dr. Mariam Hanna Oh, interesting. Okay. And when we're talking about pollen, you nicely said it really quick. So let's emphasize that again. What do we mean when we're saying the word pollen versus when we're saying spores? Dawn Jurgens So pollen is actually basically tree sperm. So trees, grasses and weeds all produce pollen. It's how they reproduce. So the pollen itself is the male component of the reproduction. The egg actually stays in the plant and the pollen is released from the plant. And then it has to travel to another plant in order to fertilize the egg. And so it will either be wind-pollinated or insect-pollinated in order to travel from one plant to another. Dr. Mariam Hanna Okay. And the wind-pollinated ones, I'm assuming, are the ones that we talk a lot about in allergy as causing symptoms. Is that correct? Dawn Jurgens Yes, exactly. And so the wind-pollinated plants, they generally produce a lot of pollen. They will produce hundreds of times the amount of pollen that insect-pollinated plants produce because it gets dispersed by the wind. And so it just needs to have a flower, because it's on the male flowers. It needs to be open to the air so that the wind can pick the pollen up and disperse it over to other plants. And it needs to produce a lot of pollen in order to be able to have the chances of getting to another female flower of the same type so that it can fertilize and produce a seed. Dr. Mariam Hanna Awesome. Okay. So in North America, we've already kind of talked about like most common trigger globally, but we're in North America. Is our most common birch or is it actually still also timothy grass, as you were saying initially? Dawn Jurgens It is birch is one of the most prevalent pollen types in terms of it produces a high amount of pollen and it is very allergenic. Pine, for example, produces a lot of pollen as well and that is generally what you see as the yellow film on your cars is usually the pine pollen. And so that occurs a little bit later in the season than the birch does, but it produces a gigantic amount of pollen. You can hit a pine tree and you will get to see big fluffs of yellow dust coming off of it. And that will be the pine pollen, but it's not highly allergenic, so it's not as worrisome for most people. But for sure, birch pollen is the one that is most relevant. Dr. Mariam Hanna Okay. What makes certain pollens and spores more likely to trigger allergies versus others? We talked a little bit about like wind pollination versus insect pollination, but are there other features of that pollen and spore that make it more likely to trigger allergies versus not? Dawn Jurgens Yeah. I mean, we did talk about anemophilous and entomophilous is the word. So anemophilous means wind pollinated. Entomophilous means insect pollinated. That is one of the major factors. Another one of the major factors is just the composition of the pollen types because certain pollen types have different allergen epitopes, they're called. And if it has the allergenic epitope, it will cause more allergenic reactions or allergy reactions. And so it is... Dr. Mariam Hanna Can you tell me more about this allergenic epitope? What makes it allergenic? Dawn Jurgens It is just because mostly it is because the IgE, the immunoglobulin in your bodies, are produced for other things. They're not really produced for pollen, but they will sometimes recognize these epitopes inside the pollen, even though that's not what they were originally produced for. And so that's why it causes the allergy reaction. It is more of a cross-reactivity phenomenon, and it's an overreaction of your immune system to the trigger. Dr. Mariam Hanna Okay, fair enough. And does the change in air quality impact these pollen and spore counts that we get from day-to-day or like heat or humidity? I imagine wind does. What kinds of things impact it? Dawn Jurgens So the air quality will impact first off as a irritant to the lungs and the immune system. So it can sensitize people to pollen a little bit more, and it'll exacerbate their symptoms. But it also can cause what they call the pollen pollution complex, where it damages the surface and makes those allergic epitopes easier to get to for the IgE antibodies. And so it increases the allergenicity of the pollen itself, and so it actually makes it worse when you have certain pollutants in the air. And then there's meteorology conditions that will also play a role in the terms of, you know, have you ever heard of thunderstorm allergies? Dr. Mariam Hanna Yeah, let's talk about that a little bit. Yes, okay. Go ahead. Dawn Jurgens And so what happens is that the pollen that's in the air will be broken apart into smaller particles. So that can be a problem for two reasons. Because when they're smaller particles, they can infiltrate deeper into the lungs, and therefore it can cause more symptoms. And it also breaks it apart and opens up those epitopes that I was talking about earlier to the antibodies, so that then it can cause higher allergic reaction. Because sometimes these epitopes are actually embedded inside the pollen, and if they're not broken apart or damaged by the pollution or by the air pressure and thunder and lightning and things like that, then it's not going to cause as much reaction because it is hidden within the pollen itself. But when they get broken apart or when the outer surfaces are damaged, then you have higher reactivity because they are going to be more available. Dr. Mariam Hanna I think these comments are really, really important to say like the air quality outside may be impacting the host itself or like us as humans in being more sensitized and already more irritated. And then to flip it to say the pollens themselves that you're being exposed to may trigger or be more likely to trigger an allergic reaction. So there's a little bit of both happening, which I don't think I appreciated as much. So that's actually very interesting to know. I want to talk about cross-reactivity of pollens, like you know which trees are related to which other trees, which grasses are related to which other grasses, mostly in terms of determining how to do immunotherapy properly or what to test for appropriately when we're doing skin testing or blood work. Can we talk about the science of how cross-reactivity is determined and what we know there? Dawn Jurgens Yeah, so it goes back to those epitopes that I was talking about because the phenomenon of allergic reactions is where the body is overreacting in the immune system. So these IgE antibodies are not specifically produced for let's say timothy grass, which is something that people are very allergic to. But it will react to timothy grass because it has similar epitopes to something that is actually a problem for the body. And so it has similar structures. And then when you have pollen that are from plants that are related to timothy grass, they will have conservation of epitopes. And so then you get cross-reactivity because it is going to recognize those same epitopes. And so you get higher reactions. And this can happen across, it doesn't have to be pollen, it can be foods. You can develop food allergies that because of being allergic to specific pollen types like apples and things like that, you can develop allergies to them as well. And so that is why things like birch and alder and hazelnut, these are related trees. They're in the same family. And so then they have the conservation in those epitopes. And so then they will react to more than one typically. Dr. Mariam Hanna Okay. And so then when I'm testing them, if they're positive to one, then it's potentially that they're going to be sensitized to the other ones because they look so similar. Is that correct? Dawn Jurgens Yes. And they look similar on a molecular scale. But also, interestingly, just because I know I look at these pollens all the time under the microscope, they actually look similar morphologically. So like they have a similar shape. They have the same number of pores and things like that. And so they look very similar as well. So you can tell when you're looking at the pollen itself that it might be closely related because it does look very similar as well. Dr. Mariam Hanna Okay. And would like molds do the exact same thing when we're talking about like mold spores and allergy to spores? Dawn Jurgens Yes, it would follow the same mechanism. And so we don't know as much about the relation between the different spores because most spores are difficult to actually speciate in terms of the morphological characteristics when you look at them under the microscope. So we have some more, we have some groups that are pretty well defined. Things like Alternaria and Cladosporium, for example, are very well defined because they are pretty unique looking under the microscope. They're also highly allergenic for a lot of people. So they are something that more research has been done on identifying them and on their specific classifications and things like that. But then there is a ton of different spores that are issues, like Basidiospores, where that is a very broad category. So Basidiospores are generally things like mushrooms and shell fungus. And so they proliferate a lot in the fall. And so that is something that we see high numbers of in the fall when the weather cools down a little bit, we get a little bit more rain, things like that happen in North America, at least I'm speaking that these these things happen. And those types of fungal spores really increase in numbers at that time. Dr. Mariam Hanna And those type of fungal spores are very, like, allergenic or they cause patients a lot of symptoms. Is that correct? Dawn Jurgens Yes, they do. And so we see actually a lot of people that think they're allergic to ragweed because of the time of their allergy symptoms. But perhaps they may not when you're testing them in your office, you may not see an actual reaction to ragweed. And then it could be, due to the history, you can figure out that maybe it's fungal spores instead because it's occurring at the right sort of time. But you may not have a Basidiospores mix that you can test with, but it's more anecdotal then that you know that it might be this that's causing the reaction. Dr. Mariam Hanna Okay. Leading me to tell you about the mystique around molds and fungal spores in my office. People become obsessed and ask for, like, should they get an evaluation of their home if there's some minute level of mold spores that might be in their home? Is that an actual thing? Can somebody be living with that amount of mold spores and not notice water damage or mold damage? Dawn Jurgens Generally, once you see water damage and mold growing, specifically black mold, which is Stachybotrys, is the black mold. That's the type that it is. Generally, when you see that growing, the mold spore count is going to be very high. By the time you see it growing, you could very well have it growing inside the walls and it could be coming out. But if you don't disturb it, it's not going to come out as much. People that are highly sensitive might be reacting, but for the general population, until you actually see it outside, because when it grows on the outside of your walls, it has free passage to just come out and get into your lungs and wreak havoc. But if it's inside your walls, it's a little bit more contained. And so the levels won't be as high. But Stachybotrys is a particular problem because it does produce a toxin that, along with being an allergen, it produces a toxin. So then that's a particular health concern. Whereas other molds, such as Cladosporium or Alternaria, they mainly grow outside. They can be inside, but they mainly grow outside in fallen trees, dead wood, leaves, rotting leaves, things like that is where you find those types of fungal spores, the fungus itself growing and then producing fungal spores. And it generally is in wooded areas and things like that you see the highest counts. When you're actually in urban environments, the counts can sometimes go up, but they're not too elevated. Dr. Mariam Hanna Okay. We generally like talking about the pollen season that patients have gone through when we see them in follow-up or in consultation. What can you give us as a generic for this past 2025 pollen season for Canada specifically? Dawn Jurgens So the past pollen season, we had ragweed being actually generally a major problem, but this year was pretty low compared to normal for ragweed. That's, ragweed is really only a problem in Eastern Canada. We really don't see much ragweed anywhere west of, you can see a bit in Saskatchewan, but not Alberta, not BC. But we had extreme heat, drought. It does not grow well in that environment. So we had very low ragweed counts this year. Spring pollen season was a bit more manageable in terms of length because we had a little bit of a slow start because it got warm and then really cold for a little while, and then it picked back up. And so the levels were actually a bit more elevated than they usually were because it was actually condensed. So what we saw was that the length was shorter and the levels got higher over a shorter period of time. So that in clinical terms could cause more reactions in more people, but for a shorter period of time. Dr. Mariam Hanna Okay. So a tough season, but a condensed season for the springtime allergies. Okay. So the Weather Network always wants to ask, and any TV channel will want to ask you, are pollen seasons getting longer? And they always ask this at the beginning of spring, where like I have no idea what the season is going to look like anyways. And I haven't talked to you to hear about your summary of it. So what would you say to that? Are pollen seasons getting longer in general? Dawn Jurgens In general, yes. I would say that they are in Canada because we have a harsh winter, right? And so then we have a defined start of our season when it starts warming up in the spring. And so the spring pollen season is coming much earlier than it did 30 years ago because we have data from over 35 years back in a lot of centers of Canada. And we can tell that it's actually starting earlier and it doesn't generally last much longer in the fall as of yet. We haven't seen that trend occurring, but we have seen it starting earlier in the springtime. So it is obviously lengthening in terms of that. And we may start to see as pollen, as the climate continues to get warmer, we may see it lengthen in the fall as well. It depends on the trends and where the warming occurs. Dr. Mariam Hanna Okay, fair enough. And how do you predict when the pollen season will start? Dawn Jurgens So the when is mainly determined by the weather in the spring. So in Canada, we have a cold winter, so it has a defined start. So in January and February, we will get usually from people like the Weather Network and Environment Canada, they'll put out their outlook for the spring weather trends. But it generally depends on if it remains cold until mid-March, it will be a delayed start of the season. If it is actually warmer in early March or even into February, it will start much earlier. So it's a lot easier to predict two, three weeks ahead than it is to predict two, three months ahead, because the weather changes so rapidly at that time of year that it's hard to predict it well in advance. Dr. Mariam Hanna Right. And the challenge we often run into as allergists is that for starting some forms of immunotherapy, you need to start two to four months before when that pollen season is expected to start. So oftentimes we're left with looking at historically, when does this start in the region that we're living in? Dawn Jurgens Yeah. And so it's a good idea to look at the extremes of starts and ends for your pollen season. And so it's a good fact that most of the worst allergens are not early starters. Things like birch is a kind of a later start. So we can know how the early pollen season is going before those two, three months period is up. So we can have a little bit more guidance on the later pollen seasons versus the earlier ones. Dr. Mariam Hanna Okay. Given your knowledge of aerobiology, are there practical tips or tricks that you would like recommend to people today to minimize their exposure to seasonal allergens? I often get left with, like, can't hide inside all day. Like that's not going to be a practical strategy here moving through the season. What tips or tricks would you offer to patients? Dawn Jurgens Okay. Well, first off, I want to just now take a moment to plug our app because knowing what is going to be in the air is very, very important because for example, like you said, people don't want to hide inside all the time, but you can know that you can look at pollen forecast and then you can determine which day might be the better day to go out and do that hike or go out and take a nature walk or something. Now, other strategies that you can use when you do go out and if it's a high pollen day, you want to try to minimize the amount of pollen that you bring inside your house because if you do things like take a shower, wash your hair every evening before bed, you're not going to transfer the pollen that's in your hair onto your pillow into your face. You can use sunglasses that kind of wrap around your face will keep pollen out of your eyes so that way it will decrease the amount of pollen that gets in your eyes and makes your eyes itchy. Obviously, use air conditioning instead of having your car windows open and very easy to do and then you want to close windows. Don't leave windows in your home open because then you're going to just be letting pollen into your house. You can use filters if you have an air exchange system or air conditioners. Run those so that it can filter out a lot of the pollen that does get into your home and pets. They bring a lot of pollen inside as well so you want to make sure and if you're able to brush them outside before you bring them into the house so that that will get rid of a lot of the pollen that they bring into your house. Dr. Mariam Hanna Fantastic and always helpful to kind of know what to look for in the season ahead even though we're going into winter. Spring shall come soon enough. All right, time to wrap up and ask today's aerobiologist Dawn Jurgens for her top three key messages to impart to patients and physicians on today's topic, aerobiology. Dawn, over to you. Dawn Jurgens So number one, don't just rely on the textbook definition of when the pollen seasons are. You need to have reliable data to know when the pollen seasons are starting, when they're ending, and when they're peaking. Number two would be to know what is in the air according to the forecast. So get an app like ours, Allergy Sufferers app, and you can know what's in the air. You can be able to track your symptoms, track your medication, all those features that are very important. And number three, don't forget to take your medication because medication is one of the best ways to actually minimize symptoms because avoidance is great but you can't, as you said, you can't hide inside all the time. So you have to be able to take your medication in order to minimize symptoms and have a good quality of life. Dr. Mariam Hanna Fantastic and have a great season ahead. Thank you, Dawn Juergens, for joining us on today's episode of The Allergist. It's so nice to be here. Thank you so much. This podcast is brought to you by the Canadian Society of Allergy and Clinical Immunology and produced in collaboration with Podcraft Productions. The opinions shared by our guests are their own and do not necessarily reflect the views of the CSACI. Please remember that this