Rising temperatures make the allergy season last longer and increase pollen concentrations, studies suggest.
The world's 6th-warmest year since 1880 was 2022. Scientists call rising temperatures the greatest threat to global public health, impacting us by exacerbating natural disasters, such as wildfires and hurricanes, and expanding the pollen season.
Authors of the 2021 study published in the PNAS examined pollen data from 60 North American stations from 1990 to 2018. They found that the pollen season across the region lengthened by 20 days on average, with the season starting earlier in the year.
Meanwhile, pollen concentrations rose by 21% in the last 30 years, with the largest and most consistent increases in pollen levels observed in Texas and the midwestern United States.
A newer 2023 report from Climate Central suggests that temperatures have been warming in 203 U.S. cities since 1970, with the freeze-free season lengthening by 15 days on average. This means plants have more time to flower and release allergy-inducing pollen.
Pollen is a fine powder produced by seed plants and an airborne allergen, exposure to which can trigger allergic rhinitis. Also known as hay fever, the condition causes cold-like symptoms, including a runny nose, congestion, and sneezing. Allergic rhinitis affects about 60 million people per year in the U.S.
Exposure to pollen can also trigger symptoms of allergic conjunctivitis, which is the inflammation of the lining of the eye, characterized by red, watery, or itchy eyes. As many as seven out of 10 patients with allergic rhinitis also suffer from allergic conjunctivitis.
The PNAS paper authors conclude that exacerbation of pollen seasons in the last three decades had harmful effects on respiratory health. This may have implications for people with asthma and other respiratory illnesses who tend to be more sensitive to pollen.