Why Your Allergies May be Getting Worse
(And what you might be able to do about it)
Sniffling, sneezing, itching, coughing: such is life for a seasonal allergy sufferer.
Every spring and summer, flowering plants produce pollen as a means of reproduction. If the plant is a wind-pollinator (rather than an insect-pollinator), the male plants release this powdery substance into the air in hopes of reaching a female plant to produce more seeds. All the pollen that doesn’t make it to its destination just hangs out in the air, eventually settling in the environment and in our airways.
Photo by Timothy Dykes on Unsplash
Although we all breathe pollen, not all of us suffer from allergies. Those who do are experiencing an overreaction of the immune system: the process that happens when your body sees a substance as harmful, even though it’s not. Your immune system then makes antibodies, and they inflame your sinuses, your airways, and even your skin.
Many people reported the summer of 2021 as their worst allergy year to date, and they aren’t wrong. A recent study shows that since 1990, the pollen season has increased by 20 days a year. And while that may not sound like much, the amount of pollen itself has increased by 21% since 1990 just in North America. The main reason is due to climate change--warmer temperatures cause flowers and plants to bloom sooner, leading to pollen production earlier and earlier every year. Plus, smog and smoke from pollution and wildfires can trap pollen in the air, leading to a longer exposure time.
Higher amounts of carbon dioxide in the atmosphere also cause plants to bloom more, according to a study published in 2016. Green-leaved plants use photosynthesis to get energy from the sun and combine it with carbon dioxide from the air. Once they combine these with water and nutrients from the ground, they produce sugars, which give them energy. The increase of carbon dioxide in the air means that plants can photosynthesize more, and therefore, grow larger and produce more pollen.
These changes don’t just affect current people with allergies--more pollen for a longer amount of time often leads to people developing allergies, even if they didn’t have them before.
Photo by Diana Polekhina on Unsplash
But climate change isn’t the only reason that pollen is on the rise.
In urban environments, city planners tend to favor deciduous male trees over female ones. This is called botanical sexism.
Deciduous male trees don’t produce fruit, so they’re easier to maintain, especially at a large scale. For years, city horticulturists have planted these male trees without pairing them with females. Since the male trees are the ones that produce pollen, they’re free to spread their dander across the environment without many female trees to trap it and turn it into seeds.
This botanical sexism isn’t a recent decision; in fact, the earliest mention of this favoritism toward male trees can be seen in the 1949 edition of the USDA ’s Yearbook of Agriculture. “When used for street plantings only male trees should be selected, to avoid the nuisance from the seed,” according to the city planners of the day. This was the first mention of favoring male trees over female ones, but it may have been going on for years before that. These “litter-free” plantings bypassed the need for fruit harvesting or seed cleanup, so while it was convenient for those who took care of the trees, it was also inconvenient for everyone’s airways.
Photo from the Biodiversity Heritage Library
Experts note that while the summers of 2020 and 2021 may have been tough for allergy sufferers, they weren’t as bad as they could have been. Mask-wearing and hand-washing saved a lot of people from breathing in the irritants that cause allergies. This means that in the future, when we aren’t wearing masks or being as cautious about germs anymore, allergy symptoms could be even worse.
Thankfully, there is a way to alleviate some of our allergy problems.
In June of 2021, the USDA Forestry Service published a report in collaboration with Thomas Ogre n, the horticulturalist who coined the phrase “botanical sexism.” This report recommends that city planners work on reducing the number of male trees and introduce more female trees to capture the pollen in the air. The report also recommends adding diversity to the landscape, and including more allergy-friendly trees.
Book by Thomas Ogren
The City of Portland still asks that street trees have "minimal fruit or seed drop."
Screenshot from Portland.gov
And, the City of Portland prefers deciduous trees because of their "showy flowers and/or fall color."
I asked Portland residents to share their experience with allergies, and whether or not they live near a street tree.
Explore the map below to see how Portland residents are affected by allergies.
Allergies and Street Trees
Survey Data Results
62% of survey participants had lived in Portland longer than 10 years, and 62% of participants suffered from seasonal allergies.
Do you suffer from seasonal allergies?
37% of participants said their allergies had gotten worse in recent years, while 25% of participants said their allergies had actually gotten better.
In recent years, how have your allergies changed?
74% of participants had a street tree outside of their home, and about half of those people knew what kind of tree it was.
Do you have a street tree outside of your residence?
Conclusion
Street trees may be affecting allergies, but more data is needed (and a bigger data pool).
Lots of factors go into an allergic response, including weather, temperature, and environment. But, as urban planners start to change the way they think about street trees, we might just see a decrease in allergic reactions over time.
Want to participate in this survey? Fill out the questions below to add your data to the map.
Seasonal Allergies in the Pacific Northwest
