Why It Feels Like Allergy Season Is Getting Longer, More Severe
Temperatures are beginning to warm up, indicating the arrival of spring -- and of allergy season for millions of Americans.
Research shows that allergy seasons may be hitting people harder by starting earlier, lasting longer and creating more pollen.
Growing seasons -- the time of year that conditions allow plants to grow -- start earlier and last longer than they did 30 years ago, according to a report from the Allergy and Asthma Foundation of America.
Additionally, pollen concentrations have increased up to 21% across North America over the last three decades, data from the USA National Phenology Network shows.
Allergists told ABC News a mix of climate change and more carbon emissions has led to plants in many areas having longer growing seasons and higher pollen counts.
"Research has definitely shown that the seasons are indeed expanding," Dr. William Reisacher, an otolaryngic allergist at Weill Cornell Medicine and New York-Presbyterian Hospital, told ABC News. "We're seeing longer pollinating seasons. We're seeing higher levels of pollen."
What causes seasonal allergies?
Allergies occur when the immune system views food, medicine, plants or something else as a harmful substance and overreacts.
Some seasonal allergies, also known as allergic rhinitis or hay fever, occur due to pollen, which are tiny grains that are dispersed from certain flowering plants.
"Allergies are essentially your immune system overreacting to things that you're exposed to in your environment," Dr. Thanai Pongdee, a consultant allergist-immunologist at Mayo Clinic in Rochester, Minnesota, told ABC News. "So, for example, if you have hay fever and are allergic to tree pollen or grass pollen this time of year, when you breathe that pollen in, your immune system recognizes it and causes a cascade of events where various chemicals get released -- one of the main ones being histamine, and these chemicals cause the symptoms that many experience."
Reactions can range from mildly annoying symptoms to life-threatening reactions including anaphylactic shock, which can cause multiple organs to fail.
As of 2021, an estimated 25.7% of U.S. adults and 18.9% of U.S. children have seasonal allergies, according to the CDC's National Center for Health Statistics.
Why are allergy seasons getting longer?
Allergy season typically begins in the spring, around March, and typically ends in the fall, lasting as late as November.
"When we refer to seasonal allergic rhinitis, we are usually referring to allergic symptoms that occupy a certain time of the year," Reisacher said.
"So, springtime, at least in the northeast, is typically when the trees are pollinating whereas in the summertime, we see the grass is pollinating, and then in the fall, it's all about the weeds," he continued. "Ragweed is the most common pollen present at that time of the year."
However, research has suggested that allergy seasons are getting longer and worse.
"Allergy season is getting longer -- in fact it is an average of 13 days longer compared with 20 years ago," Dr. Purvi Parikh, an allergist and immunologist at NYU Langone Health, told ABC News.
A 2022 study from the University of Michigan found that, by the end of the century, pollen emissions could begin 40 days earlier in the spring than occurred between 1995 and 2014, meaning there could be an additional 19 days of high pollen counts.
Allergists say climate change is one of the biggest reasons why allergy seasons are getting longer.
A 2021 study found human-caused climate change is worsening North American pollen season, causing them to lengthen by 20 days on average between 1990 and 2018.
Reisacher said that as the globe experiences warmer temperatures each year, more storms are occurring, which kicks up more pollen.
"It travels for many more miles on the wind, and it makes it more allergenic, so it gets deeper into our body, into our lungs and even through the tissues that protect our body," he said.
The warming planet also means that it's taking longer to see the first frost, which usually occurs in the fall and hold pollen underground, he said. A longer time to get to the first frost means pollen has a longer time to stay in the air.
Reisacher said greenhouse gases are another reason for the longer allergy season. He said more carbon dioxide has been released into the air due to fossil fuels. Plants feed off carbon dioxide, and this has released more pollen into the air.
"There has been a direct correlation between the levels of [carbon dioxide] in the atmosphere and the amount of pollen that plants, including ragweed, are producing," he said. "So, it's hard to deny that that is a factor."
Reisacher and Parikh say this means there will likely be more people who experience seasonal allergies over the next several years.
How to treat seasonal allergies
Allergists said there are a number of over-the-counter medications that people can try as well as nasal sprays and rinses.
Some are tailored to relieve symptoms while others are used to prevent symptoms. Additionally, only certain medications work for certain symptoms.
"Start with 24-hour antihistamines. They last longer with fewer side effects," Parikh said. "[You] can also add nasal steroid or antihistamine sprays as well as eye drops. However, if you aren't improving, please see an allergist."
Pongdee said allergy shots may be effective for those who are looking for long-term solutions and are not relief from daily medication.
Reisacher recommends starting medications a few weeks before allergy season starts because they need time to take effect.
He said there are also steps people can take to at home to prevent pollen from coming indoors including keeping windows closed in the early morning when pollination is higher, using air conditioner filters. separating indoor and outdoor clothing and showeing to get pollen off skin and out of hair.
"You want to create a safe haven, and that's your bedroom," Reisacher said. "You want to create a pollen-free environment in your bedroom so that at least you have seven or eight hours that your immune system can rest without having to react to pollen."
