Climate change leads to longer pollen seasons, more allergies


Climate change means more than stronger, more ferocious weather and hard-to-contain wildfires. Here's what it means for allergies.

A report in early August 2021 from the Intergovernmental Panel on Climate Change did not paint a rosy picture for the future. Instead of detailing progress from recent years of effort to improve air quality, the international group declared that massive and unprecedented climate change has touched every corner of globe. And although current efforts may immediately improve air quality, it will take decades to reverse global temperatures shifts that are changing our climate.1

What does this have to do with respiratory allergies in Everytown, USA? Everything, according to experts.

Climate change and global warming have changed weather patterns, prompting changes to growing seasons and pollen behaviors.

One study published in 2020 revealed that it’s not as simple as a change in growing season, either. Plants have enhanced photosynthesis and reproduction, therefore producing more pollen, as carbon dioxide levels in the atmosphere rise. Thunderstorms can exacerbate pollen irritation in hay fever season, the report continues, and floods and increased rain help asthma-inducing molds proliferate. Combined, these effects significantly worsen respiratory symptoms for people with allergic respiratory diseases like rhinitis and asthma, the study concludes.2

William R. L. Anderegg, PhD, associate professor of biology at the University of Utah in Salt Lake CIty, agrees. Anderegg was lead author on a 2021 report that detailed significant increases in pollen counts between 1990 and 2018, especially in Texas and the Midwest in the spring. Tree pollens had the greatest increase, pollen seasons overall were longer by the end of the study period overall.3 According to the Asthma and Allergy Foundation of America, warmer temperatures extended the length of the pollen season in the United States by 11 to 27 days between 1995 and 2011.4

“Pediatricians and allergists need to be prepared that pollen seasons are starting earlier over time,” he says, adding that education about these changes is important to help patients stay ahead of the game when it comes to medications.

Patients and parents should be encouraged to know their allergens, and have their medications on-hand at the onset of the offending pollen seasons in their area.

“Overall, one of the most crucial things we can do is to tackle climate change as quickly as possible to reduce these impacts on respiratory health,” Anderegg says. “Longer pollen seasons and higher pollen concentrations are just one example of how climate change is having substantial impacts on our health already.”

Pollen is just one piece of the puzzle, climate change is also increasing the prevalence of other respiratory irritants. Warmer temperatures increase the concentrations of air and water pollutants, according to the Centers for Disease Control and Prevention. Increased air pollution—as well as increases in temperature and ground-level ozone—can exacerbate conditions like asthma and chronic respiratory disease. Even in people without existing respiratory conditions, concentrated air pollution caused by climate change can contribute to inflammation and lung damage.

Although pediatricians can do little to impact climate change on a practice-level, national organizations can support efforts to address climate change. On the smaller scale, pediatricians can educate parents and patients on how to gauge air quality and track pollen counts, and when to start or resume medications for the best effect.


1. Intergovernmental Panel on Climate Change. (2021.) Climate change widespread, rapid, and intensifying. Published August 9, 2021. Accessed August 11, 2021.

2. Anderegg WRL, et al. Anthropogenic climate change is worsening North American pollen seasons.PNAS. Feb 2021, 118(7). doi: 10.1073/pnas.2013284118.

3. D'Amato G, Chong-Neto HJ, Monge Ortega OP, Vitale C, Ansotegui I, Rosario N, Haahtela T, Galan C, Pawankar R, Murrieta-Aguttes M, Cecchi L, Bergmann C, Ridolo E, Ramon G, Gonzalez Diaz S, D'Amato M, Annesi-Maesano I. The effects of climate change on respiratory allergy and asthma induced by pollen and mold allergens.Allergy. 2020 Sep;75(9):2219-2228. doi:10.1111/all.14476.

4. Asthma and Allergy Foundation of America. Climate and health. Accessed August 17, 2021.

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