Graphic by Olivia Chester
When Raleigh native Ben Shifman went to dinner with his girlfriend in Carrboro, a thick layer of yellow pollen coated the table and silverware. A lifelong sufferer of pollen allergies, Shifman began to have trouble breathing. He made it through dinner with the help of an inhaler, but during a post-meal walk, Shifman became nauseous.
“I hope I don’t yack,” he said, handing a box of leftovers to his girlfriend.
Moments later, Shifman ducked into an alleyway to vomit — an allergic reaction he’d never had before. He said his allergies have been particularly bad this year, with a noticeable difference between North Carolina and other states.
“I travel quite a lot to South Carolina and Georgia, and the pollen in North Carolina was so insane,” Shifman said. “Coming back to Raleigh, my parents’ house is just covered head-to-toe with yellow pollen. I can’t wait for the season to be over.”
For several days in March, yellow pollen clung to seemingly every outdoor surface: sidewalks, cars, benches. While that initial blast of yellow pollen is gone from view, washed away by rain, pollen season is far from done. And the factors that potentially caused this boom — warmer weather, milder winters — are here to stay.
According to a 2023 press release from the Centers for Disease Control and Prevention, about a fourth of adults in the United States have seasonal allergies. Dr. Edwin Kim, chief of the UNC Pediatric Allergy & Immunology division, said that allergies are an overreaction of our immune system, which is designed to fight off foreign material like bacteria and viruses.
“But for people who are allergic, their immune system sees things like pollen — that should be otherwise perfectly safe and benign — and thinks that they’re bad and develops antibodies specifically against it,” Kim said.
These antibodies float around in our bloodstreams, waiting for exposure to pollen before releasing chemicals like histamine which cause the symptoms associated with allergies: congestion, runny nose, itchy eyes, coughing, wheezing and more. Greg Copenhaver, a UNC-Chapel Hill biology professor who researches plant genetics, said that it’s the proteins on the outside of the pollen molecules that people are allergic to. These proteins are essential for fertilization, telling plants to accept the pollen that lands on them.
“It just happens that because [the proteins are] so abundant in our environment in an airborne way, that we become sensitized to them and [they] become allergenic,” Copenhaver said.
All the yellow pollen outside, which comes from pine trees, isn’t actually that allergenic due to the larger size of its molecules and smaller number of proteins.
“They’re kind of cute when you look at them under a microscope,” Copenhaver said of pine pollen. “They look like Mickey Mouse — they’ve got a round part and then two ear-like structures on them.”
Fellow UNC-CH professor and paleobotanist Patricia Gensel’s description is more direct: Each pollen molecule has a central body and two small bladders. Pine pollen is a couple of hundred micrometers large, she said, compared to the more allergenic oak pollen, which is 50 micrometers and has more proteins. Oak pollen’s smaller size allows it to infiltrate the body better, and its increased protein count — its flowers are pickier about which pollen to accept — induces stronger reactions.
Shawn Taylor, a public information officer from the N.C. Division of Air Quality, wrote in a statement to UNC Media Hub that it’s difficult to define a start or end to pollen season because pollen activity depends on varying factors like plant species, weather and geography. But generally, spring is when trees pollinate: first junipers and cedars, then oaks, pines and maples. In summer, tree pollen decreases, replaced in prominence by grass pollen — considered the most allergenic — and then by weed pollen in the fall. People can be allergic to some pollen types and not others.
The weed pollen stays until the year’s first hard frost, when the temperature dips below 28 degrees for at least a few hours. Tree pollen season begins when the weather warms again. However, as temperatures in North Carolina stay warmer for longer, pollen season has both started earlier and ended later than it did in past decades.
“For someone with a classic seasonal pollen allergy, you used to get a little bit of relief for two or three months in the wintertime,” Kim said. “Now, we’re lucky to have a month of no pollen.”
In addition to being longer, Copenhaver said pollen seasons are getting more intense. He said multiple factors can influence pollen’s creation and dispersal. For instance, a hard downpour will knock pollen out of the air, but light sprinkles over a longer period can encourage pollen production as plants utilize the moisture to pollinate. Copenhaver also said more carbon dioxide in the atmosphere aids plant photosynthesis, allowing them to produce more flowers which produce more pollen.
Gensel and fellow UNC-CH professor Robert Peet, who specializes in plant ecology, agreed with the general observation that there was a lot of visible pollen this March.
“It’s an extreme year,” Peet said. “[Gensel and I] haven’t experienced anything quite this extreme in the nearly 50 years we’ve lived here.”
Peter White, another professor at UNC who researches plant ecology, wrote in an email to UNC Media Hub that while warmer temperatures could speed up plants’ developmental processes, thus shortening pollen’s dispersal period, increased pollen density during a particular time — like those yellow-tinted weeks in March — doesn’t necessarily mean the total amount of pollen in a season has grown.
Gensel also said that the pollination process was condensed this year. The latter months of 2024 were mild. Then, North Carolina had a burst of cold — the snow in January and February — followed by a quick warming. She said this made plants shed their pollen at the same time instead of during a spread-out period.
“We went from sort of feeling nothing to, all of a sudden, it all coming out at once,” Kim said. “It was a double whammy that really knocked people over.”
Peet said that the mild winter, with lots of decomposition and more nutrients in the soil for trees to soak up, could have stimulated a mast year: a mechanism among certain trees to avoid having all their seeds destroyed by overproducing them in one year, with the following years seeing very little seed production. But what if we continue to see these milder, shorter winters?
“There could be a climate change thing here, where this may become more frequent because the trees have not evolved in the context of this warmer environment,” Peet said. “So, they’re behaving differently than in their normal situation.”
Gensel said that this could be OK, as long as there are enough nutrients so that the trees don’t become stressed. Regardless, Peet dismissed the possibility of consecutive mast years. Even with extra resources, these trees cannot compensate for the energy used from this mast year; they must recuperate first. It’s possible that, even if the weather trends that potentially caused the pollen bloom continue, North Carolina still won’t see another event like this for a few more years as plants restore their energy.
In the meantime, Gensel said the excess pollen shouldn’t have a negative effect on the ecosystem. Peet said the area may see a burst of new trees and the animals that feed off them, like squirrels. Otherwise, humans may feel the most affected. Gensel had to wash her car three times and scrub off her house’s deck; Peet’s deck is still covered in pollen despite the rain, which just clumped it all together.
When it comes to allergies, Kim suggested that people minimize their exposure to pollen. While avoiding it entirely is nearly impossible, he said to plan outdoor activities around what times are most allergenic. Pollen counts tend to be higher in the early morning and peak midday. The N.C. Division of Air Quality operates a pollen monitor in Raleigh, releasing a daily report that users can subscribe to on its website. Driving with the windows down, washing up after coming inside and wearing a mask can also help lessen the effect of pollen.
Kim said nose sprays are the best medicine but work much slower than antihistamine tablets. Allergy shots, he said, are the most effective medical solution. The treatment plan is long — four to five years — but the exposure therapy retrains the immune system to tolerate pollen. Kim received allergy shots several years ago and hasn’t had to use any other allergy medicine since.
Although yellow pine pollen doesn’t adorn every outdoor surface anymore, microscopic allergens are still in the air, and grass pollen season is set to begin soon. North Carolina’s diverse plant ecosystem, set against warming weather, may continue to beleaguer residents, especially those with allergies.
“One of the reasons we love coming to North Carolina is because of the outdoors,” Kim said.” But that’s also one of the reasons there’s so much pollen allergy.”
