Climate change lengthening pollen season, making allergies worse

On a warming planet, allergy season is getting worse, experts say.

Spring allergies are starting earlier; fall allergies last longer. With climate change causing allergen culprits including trees, turf grass and weeds to release pollen longer than in the past, experts say more research is needed to better predict pollen counts and prepare vulnerable populations — which include 25% of adults nationwide who have a seasonal allergy, according to the Centers for Disease Control and Prevention.

“Climate change is causing some plants to bloom and release pollen earlier leading to a longer duration of 'pollen season': Some flowers will be early and could bloom for longer, and some will flower more in line with historic times leading to a longer season overall,” Taran Lichtenberger, the Budburst Community Engagement Manager with the Chicago Botanic Garden, said in an email. “Observations of plant flowering times across the season show this trend.”

Allergies are caused by plants that are wind pollinated such as trees, grass and shrub species, as opposed to plants pollinated by insects or other animals, Lichtenberger said.

Kentucky bluegrass, one of the most common grass species in lawns, is also one of the most common pollen allergens. While grass pollinates in May and June, street trees — including ash, maple and oak — tend to kick off allergy season in March and April.

As for late summer and fall, weed pollination leads to “back-to-school allergies.” Ragweed, mugwort and sagebrush release pollen beginning in mid-August through September. Ragweed is particularly widespread in Illinois, and the plant often continues to produce pollen until the first frost.

Allergy symptoms will last for as long as the allergen is in the air, and should go away a few hours after exposure.

With seasonal allergies on track to intensify, Dr. Christina Ciaccio of UChicago Medicine said those who suffer from pollen allergies should continue following routine treatment, starting with antihistamines and graduating to nose sprays if symptoms persist.

If over-the-counter sprays don't provide relief, Ciaccio said a visit to an allergist for allergy shots — which work much like vaccines — might be in order.

Everyday habits that can help protect from prolonged pollen exposure include taking a shower and changing into fresh clothes when arriving home from a day outside as well as washing bed sheets with hot water, which helps to break down pollen protein.

The close relationship between climate change and pollen count has been well-documented over the last several years, but “this is only the beginning,” said Kai Zhu, an associate professor of environment and sustainability at the University of Michigan.

Research is still relatively recent, and more work is needed to develop what Zhu called the “understudied” issue. For instance, there are less than 100 pollen counting stations across the entire United States.

“You can imagine the vast space between them,” Zhu said. “If we are talking about getting a short-term forecast for pollen, we really need to have a much denser network.”

One of those pollen counting stations sits atop a University of Chicago building in Hyde Park, through which Ciaccio can access data via recently developed AI-powered technology. Whereas counts previously had to be taken in-person each day, the new method allows for remote access.

“As that is happening, I suspect we'll be able to put pollen counters in more locations because we don't necessarily have to be at the pollen counter physically every day. We can read it just from our computer,” she said. “And as that happens, I think the predictions in general will start getting much, much better.”

With more data, Zhu envisions a future where there are robust, reliable and local pollen prediction counts that can be accessed day-to-day by people who struggle with seasonal allergies, much like checking the weather.

“We need to enhance the understanding and prediction of both pollen and fungal spores for allergies — in the short term and also in the long term,” Zhu added. “Climate change is a long-term phenomena. ... We need to have a better understanding of the long term, because this is an area where climate change has a huge impact on human health.”

• Jenny Whidden is a climate change and environment writer working with the Daily Herald through a partnership with Report For America supported by The Nature Conservancy. To help support her work with a tax-deductible donation, see

Common street trees such as ash, maple and oak tend to kick off allergy season in March and April. Associated Press file photo
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