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This week marks the beginning of “peak bloom” — the time when most of the Yoshino cherry blossom trees around the Tidal Basin and throughout the city will start showing their delicate pink blossoms. That’s exciting news for many tourists and District residents, both of whom will show up to the Mall in droves until the petals have all turned to green leaves.

But while lots of people are celebrating, some are too busy sneezing. The blooming of the cherry blossom trees aligns with the flowering season for other plants and trees in the D.C. region. Those who suffer from springtime pollen allergies may start to feel the familiar onset of congestion and itchy eyes. 

Over the past century, the cherry blossoms’ “peak bloom” date has gotten earlier on average. That’s because temperatures have gotten warmer as fossil fuels have increased the levels of carbon dioxide and other greenhouse gasses in the atmosphere. And earlier blooms mean longer allergy seasons.

Washington, D.C., has seen its average allergy season increase by 20 days since 1970, according to a new analysis by Climate Central. (Graphic by Climate Central)
Washington, D.C., has seen its average allergy season increase by 20 days since 1970, according to a new analysis by Climate Central. (Graphic by Climate Central)

The District’s allergy season has lengthened by an average of 20 days since 1970, according to a study released by Climate Central on March 8. Nationally, the report found, U.S. cities have seen about 15 days added to their allergy seasons. 

Another report released this month — the Asthma and Allergy Foundation of America’s “2023 Allergy Capitals” report — actually lists D.C. as one of the best U.S. cities when it comes to seasonal allergies. The organization uses pollen counts, number of allergy specialists and amount of over-the-counter allergy medicine used to make its determinations. In a ranking of 100 cities where number one was the worst, the District came in 96th place. 

But that statistic may be little comfort to Washingtonians stocking up on tissue boxes and antihistamines this week. On average, D.C.’s allergy season — defined as the time of year when no days fall below freezing — lasts about 236 days.

What Does Climate Change Have to Do with My Runny Nose?

Experiencing warmer temperatures for longer periods causes increased exposure to both pollen from growing trees and spores from outdoor mold, both of which are common triggers for seasonal allergies.

The mold that forms in soil and decaying plants releases tiny airborne spores into the air, and some kinds can cause allergic reactions. Most types of mold thrive in summer and fall but go dormant in colder temperatures. Longer growing seasons and milder winters may mean more exposure to mold spores. 

Additionally, higher levels of carbon dioxide in the air — which is what causes climate change and warmer average temperatures — can enhance plant growth, according to Climate Central’s report. Several lab-based studies have found that higher levels of carbon dioxide, or CO2, sometimes boost the amount of pollen or spores produced by certain allergenic plant and mold species. 

Allergies are Annoying, Sure, But Why is This a Big Deal?

Many people experience seasonal allergies as a nuisance. But for asthma sufferers, especially children, they can become dangerous. The most common trigger for asthma is allergens.

In general, people experience allergies when the body responds to an unknown substance as if it’s a threat. The immune system creates antibodies that identify the substance and react to get rid of it the next time the person gets exposed, which is what causes symptoms such as itchiness, congestion and fatigue. 

For people with allergy-triggered asthma, that same reaction happens in the lungs and airways. They may experience shortness of breath, chest pain and wheezing in addition to typical allergy symptoms. In some cases, allergens may trigger full asthma attacks, which can be dangerous — particularly among children, whose smaller airways become more easily blocked.

If you’ve been here on the Our Earth page before, you’ll recognize a theme: Climate change will cause outsized harm to people and communities of color, not just globally but right here in the District. In the U.S., Black and brown folks will disproportionately face impacts like flooding, extreme heat and air pollution.

And this is true for allergies, too, because asthma impacts Black residents of D.C. at far higher rates than white residents. According to CDC data, about 9% of white adults in the District have an asthma diagnosis, while about 14% Black adults here have one. Meanwhile, at least 15,900 D.C. children suffer from asthma, and more than 72% of them are Black, according to a study published in the Journal of Asthma last year. Thus, even though everyone will experience a longer allergy season, Black families in the District will be more likely to face the most serious consequences of the lingering pollen and mold.  

What to Do About It?

Ultimately, the world needs to limit greenhouse gas emissions and slow down climate change in order to keep allergy seasons from getting longer and more forceful, the Climate Central report said. But in the meantime, families can take some concrete steps to limit the impact of allergy symptoms, especially for children and adults with asthma:

  • Before walking outside, check online for allergen forecasts and air quality reports.
  • Close windows and doors to limit pollen and spores from entering the home.
  • Keep humidity low inside homes to prevent mold from growing.
  • Make sure kids with allergy-triggered asthma can access an inhaler or other medication if they will be playing outdoors during high-pollen days.
Kayla Benjamin photo

Kayla Benjamin

Kayla Benjamin covers climate change & environmental justice for the Informer as a full-time reporter through the Report for America program. Prior to her time here, she worked at Washingtonian Magazine...

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