Climate change is making allergy season last longer

As warmer weather has spurred a boom in pollen production, it's prolonged what might very well be everyone's least favorite time of year: allergy season.

One side effect of milder winters and increased annual average temperatures is that plants not only begin producing pollen earlier but also that they produce it for a longer period of time.

"This really shows another marker of how climate change could be influencing people's daily lives," said Allison Steiner, a professor of atmospheric science at the University of Michigan. Between 1990 to 2018, the North American pollen season lengthened 20 days and pollen concentrations increased more than 20%, according to a 2021 study published in the academic journal Proceedings of the National Academy of Sciences of America. And the dreaded allergy season is likely to drag out even longer as temperatures continue to rise.

Some parts of the U.S. have already seen allergies flare up as much as a month earlier than usual. Steiner projected that the pollen season could begin anywhere between 10 and 40 days earlier and end 5 to 15 days later by 2100. Warming temperatures, in conjunction with changing rainfall patterns and rising atmospheric carbon dioxide levels, could cause plants' pollen production to triple by the end of the century, the University of Michigan team said in a report last year. That's bad news for the 81 million people in the U.S. that suffer from allergic rhinitis - the medical term for seasonal allergies.

Pollen allergies are set off when the immune system mistakes pollen as a dangerous intruder and overreacts by producing antibodies to fight it off. That's why the resulting symptoms - sneezing, fatigue, a runny nose and irritated eyes - can feel similar to a cold, the flu or even Covid.

Climate change is likely to make those symptoms worse. Longer pollen seasons and higher concentrations can cause more sensitivity to allergens, according to the Centers for Disease Control and Prevention. Continued pollen exposure can also trigger existing respiratory conditions like asthma, potentially leading to asthma attacks in which airways swell and make it hard to breathe.

This year, a warm winter has already caused earlier pollen production in some parts of the U.S. But in the Northeast, a recent storm will likely pause pollen production until the weather warms up again, said Maria Streck, a clinical instructor of allergy and immunology at the Medical University of South Carolina.

"As soon as things start to warm up, shortly thereafter we start seeing the pollen come out," Streck said.

Though there's no clear solution to the pollen boom, there are steps cities can take to mitigate seasonal allergies, said William Anderegg, an associate professor at the University of Utah's School of Biological Sciences who wrote the 2021 study on the increase in pollen over the past few decades.

Plants release pollen, grains of reproductive material, to be carried by the wind or pollinators like bees. Planting tree species that rely on insects instead of the wind to grow could reduce the amount of pollen that ends up in the air. Cities can also plant more gender diverse trees. ( Urban planners often plant male pollen-producing trees, because female trees drop fruits and seeds that can make a mess on city streets.)

A national pollen forecast, much like air quality monitoring, could also keep sensitive groups from inhaling too much pollen.

Consumer health and pharmaceutical industries are aiming to take advantage of increased demand for allergy products. French pharmaceutical company Sanofi, which makes allergy treatments Allegra and Xyzal, said in a release last year that respiratory allergies were among the "main health consequences of climate change." A Sanofi spokesperson said that the company sees "much potential within the allergy market," particularly when it comes to over-the-counter treatments.

Kleenex even launched a new line of "Allergy Comfort" tissues two years ago after the company recognized that younger consumers were suffering from more allergies than older generations, said Alison Lewis, the chief growth officer for Kimberly-Clark, which owns Kleenex.

"What we're seeing is that allergies are becoming more of a year-round health issue," Lewis said.