The US will face a longer allergy season

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By Julliana Bravo
Environmental Journalism, the University of Connecticut
April 22, 2023

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Towns and cities across the United States are expected to have fewer freeze-free days, leading to a more extended allergy season. 

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According to a recent report by Climate Central, temperature data show that freeze-free periods have increased by 15 days since 1970. Brooke Lappe, a doctoral student at Emory University, said a freeze-free day is a day in which temperature does not go below 32ºF. In agriculture, freeze-free days indicate the start of the growing season. The warmer temperature is an indication to plants to start flowering and produce pollen. The earlier the freeze-free days occur, the earlier plants flower and produce pollen. Pollen is the main culprit for seasonal allergies for many Americans. 

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Lappe also said climate change has elongated the allergy season—a warmer year caused by climate change has caused pollen production to begin earlier. However, it isn’t the same in all parts of the United States. In Connecticut, for example, allergy season began around mid-March where in previous years, it would typically start in April. Shown by this graph, freeze-free days have increased by 22 since 1970 in Hartford. In Atlanta, where temperatures are generally warmer over the year, allergy season started at the end of January or the end of February where it usually would begin around March, Lappe said.

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Higher levels of carbon dioxide also ‘super-charges’ plant growth, Lappe said. Laboratory and research studies have shown an increase between CO2 and pollen production. CO2 can increase photosynthesis in plant species that use a C3 photosynthetic pathway, Lappe said. “Rising levels of CO2 in the atmosphere can cause plants to produce more pollen,” Lappe said.

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Climate change has also caused an increase in extreme weather events such as thunderstorms. Paula Schenck, director of indoor environments and health programs, said this puts vulnerable populations at risk for water damage in their homes which increases risk of mold developing indoors. If those homeowners have nowhere else to live, they will have to reside in their unsafe home, said Schenck. Thunderstorms and mold are another way climate change can affect human health. Although thunderstorms in themselves don’t increase pollen production, it breaks the pollen down even further to facilitate entry into the lungs, Lappe said.

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“One of the obvious effects of climate change is that it’s getting warmer earlier in the year,” Pamela Diggle, the department head of ecology & evolutionary biology at the University of Connecticut, said. The earlier spring temperature causes plants to flower earlier, Diggle said. 

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Diggle said that wind-pollinated trees, such as oak, birch, poplars, beech, and pine, are the type of trees that cause seasonal allergies. A wind-pollinated tree produces dry pollen that doesn’t form in clumps. Diggle said that the way pollen dangles from oak trees makes it easy for the wind to pick up pollen. Some flowers also start budding before the leaves do, leaving nothing to block the wind along the way. Diggle also suspected that homeowners are more inclined to plant male trees, which produce pollen, as opposed to female trees, which have fruits, because of the maintenance female trees require.

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Climatologists and plant and tree experts aren’t the only ones that have noticed a longer allergy season. According to the Asthma and Allergy Foundation of America, 26% of adults and 19% of children suffer seasonal allergies. Symptoms of seasonal allergies range from congestion, sneezing, itchy eyes, and a runny nose, and can affect people to different degrees.

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Meg Walsh, an ecologist at USDA, suffers from severe seasonal allergies. Walsh recalls her allergies being severe ever since she was a teenager. Every year around April, she experienced eye and nose swelling as well as coughing. Her allergies were so bad that a routine allergy shot, an injection with a small amount of the allergen in hopes of building immunity to the allergen, sent her into anaphylactic shock. 

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Walsh said she loves being outside and in nature. However, no matter how many antihistamines she is on during the springtime, she needs to limit the amount of time she spends outdoors. Walsh doesn’t see a difference in her allergies when she travels to different towns and cities because she finds that horticulture trees which produce allergenic pollen are everywhere. However, when she has the chance to travel to the tropics, she feels fewer symptoms of seasonal allergies, she said. Walsh knows her allergies will start in April, so she takes preventive measures such as antihistamines, inhalers, and eye drops. However, this year spring came too early and she was unable to do so.

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Pamela Angelillo, a registered nurse at UConn Health, said that she started seeing patients with symptoms of seasonal allergies in February instead of in mid-March. She also mentioned the extension of allergy season might become a problem for seasonal allergy sufferers and even those who don’t have seasonal allergies. “People could have no [seasonal allergy] symptoms five years ago, but bodies change,” Angelillo said. Skin testing and allergy shots are the most common for patients with more extreme symptoms, Angelillo said.

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Dr. Kevin McGrath is an allergist in Wethersfield, Connecticut. He said seasonal allergies cause several issues in his patients, such as fatigue and nasal congestion that can disrupt a peaceful sleep. Although patients might sleep for the recommended eight hours, they will wake up tired, sore, and achy, said McGrath. He also said patients could become resistant to medication because of how frequently they take them. However, McGrath believes that studies on the relationship between global warming and the longer pollen season are not definitive yet and still debatable. 

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Angelillo has some advice for seasonal allergy sufferers. First, taking a shower before bed can help get rid of the pollen on your body and out of your hair. If you garden or do lawn work, wearing a mask can help prevent breathing in the pollen. She also advises not to sleep with the window open as it can bring pollen from outside into your home. Lastly, she recommends nasal rinses to flush out any pollen that might be trapped in your sinuses from the day.

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Lappe wrote her doctoral dissertation on the relationship between pollen, climate change, and the risk to vulnerable populations. Lappe said that those vulnerable populations include children, elderly, and Hispanic and Black communities. 

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“The sudden rise in environmental pollutant levels due to industrial development and urban motor vehicle traffic has affected air quality and consequently, the severity and mortality from allergic diseases” said a study published in the National Library of Medicine. Those exposed to traffic pollution typically live in urban areas, most of which are minority groups, Lappe said. 

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“When you add an environmental exposure, you increase risk,” Lappe said. Past research has also focused on the age trend in emergency department visits, but not a race trend, Lappe said. Indicating the importance of conducting more research. 

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While seasonal allergies affect people from all over, Connecticut has been a hot spot for those who suffer from seasonal allergies. The Allergy and Asthma Foundation of America lists Hartford and Bridgeport among the Top 100 worst asthma and allergy cities in the nation. Dr. Angelillo said that this could be because of the types of trees in that area that produce a lot of pollen, like Maple and Juniper. Schenck said that this list reflects the qualities of housing in urban areas and the burden that air pollution has created in urban areas as well. Right now, humans are left to adapt to the outside environment to reduce their own risk. “Because addressing the root cause is so difficult, we have to rely on adaptation.” Schenck said.

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