It seems everyone is sneezing, itching and blotting a runny nose these days. Allergy season comes every spring, but somehow it seems worse.

Tree and grass pollen counts have been up in the past week or two, but pollen has been making a quiet climb for years. It’s up 21% since 1990, according to the Asthma and Allergy Foundation of America.

Climate change is a culprit across the country, with longer and hotter season adding to the pollen count.

Baltimore, though, ranks 28th out of 100 for the worst areas for allergies, according to a report from the foundation, which also considers the number of people who take medications and the number of allergists available. There are a few possible reasons, experts say.

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“Climate change, impervious surfaces, male trees,” said Meghan Avolio, an associate professor of earth and planetary sciences at the Johns Hopkins University who studies urban environments. “Nothing is definitive, but there is something to all these.”

Let’s take these factors one at a time.

What do male trees have to do with allergies?

There is something called “botanical sexism,” where those in charge of planting trees in cities and suburbs, plus private landowners, have turned to male trees that make pollen over female trees that make seeds.

That’s because female trees are messier and smellier than their male counterparts. They have flowers and pods that can drop on the sidewalk.

Planting male trees was even official U.S. Department of Agriculture guidance beginning in 1949, according to the allergy foundation.

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TreeBaltimore, a group city agencies and nonprofit organizations that work to build the city’s tree canopy, reports that it regularly plants two types of male trees: honey locusts and gingkoes.

Also, “most tree species found in the city are monoecious, which means a single tree will have both male and female flowers,” said Sam Seo, acting chief of forestry for the Baltimore City Department of Recreation & Parks.

That means they produce pollen that is carried by a breeze from one branch to another, as opposed to between trees by butterflies, bees or other insects. That breeze can keep carrying the pollen right to your nose.

You can see the group’s tree inventory here.

What about the sidewalks?

Seo said all the concrete and asphalt is another factor that may be at play in cities like Baltimore.

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“I would venture to say that the amount of impervious surface in the city likely contributes to the movement and availability of pollen in the air, whereas natural areas and bodies of water might effectively capture those particles,” he wrote in an email.

The evidence: that yellow gunk that collects on top of everything.

It feels so bad now because it’s hot enough here to make everything bloom.

“There is a temperature cue, it signals trees and plants when to flower,” Avolio said.

But she said, “It shouldn’t impact how much pollen we are exposed at any time, but when.”

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Typically trees launch the spring allergy season, then grass and then weeds by fall. But trees and grasses are both making people run for the tissue box at the moment.

Are more people suffering?

Dr. Jonathan Matz, a longtime allergist at LifeBridge Health, said more people are feeling the pollen these days.

To have allergies, people have to be born with a genetic predisposition. That’s about 30% to 45% of the population, he said. Then something triggers the allergies to start — maybe a bad cold or a lot of time under an oak tree that amps up the immune system, Matz said.

The reasons aren’t really known. But in the cities and suburbs, lifestyle is likely playing a role. People don’t grow up on farms getting exposed to natural toxins and bacteria; rather, they live in sealed houses for energy efficiency and “that may have left us more susceptible.”

But usually the symptoms can be mitigated with over-the-counter antihistamines, including Zyrtec, Allegra and Claritin, plus allergy eye drops, Matz said.

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“If they don’t do the trick, it may be time to come see an allergy specialist,” he said.

Matz said he doesn’t expect a lot of focus on a cure anytime soon, as environmental allergies are typically annoying and not life threatening.

“We’ll probably be dealing with this for the next 100 to 200 years.”

Meredith Cohn is a health and medicine reporter for The Baltimore Banner, covering the latest research, public health developments and other news. She has been covering the beat in Baltimore for more than two decades.

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