If it feels like your seasonal allergies are afflict you later into the year than they used to, you’re not imagining things.
“Typically, I would not see in my patients allergies out to this time of the year,” said Dr. Kari Nadeau, a practicing allergy-immunology specialist at Beth Israel Deaconess Medical Center and the chair of environmental health at Harvard School of Public Health.
“It is absolutely a thing that we are seeing more and more,” Nadeau said. “Not just in our country or in Boston, but all around the world.”
Experts say climate change has contributed to the extended allergy season.
“I think we’re seeing this as a gradual shift over the last several decades,” said Dr. Aleena Banerjee’ clinical director of the Allergy and Immunology Unit at Massachusetts General Hospital. “And certainly in the last two decades, the data suggests is that we’re around 20 days longer in the New England area compared to where we were 20 years ago, in terms of the number of days that we’re seeing pollen present.”
That expansion happens both by starting the allergy season earlier in the spring and by pushing it later into the fall.
“Plants are now growing in areas that they weren’t able to grow in before,” Nadeau said. “And when the season is continuing to be warm ... then the plants continue to grow and pollinate. So they’re getting confused and they want to spread their seeds and grow more.”
Research at Walden Pond has shown that leaves are emerging in some species two weeks earlier than they did when Henry David Thoreau was there in the 1850s.
Increased carbon dioxide in the air also helps plants to grow, leading to more pollen, Nadeau said.
“In addition, what happens is because there’s increased carbon dioxide, mostly due to diesel exhaust emissions, that carbon dioxide then changes the chemistry of the pollen being attached to the plant, and that carbon dioxide allows the pollen to be taken off the plant much faster and much sooner,” she added.
Despite the mild temperatures in the forecast this week for Greater Boston, this fall overall has not been unusually warm. But the region has seen the second driest September-October combination on record, meaning that allergens may not be cleaned out of the air as much as normal.
And, Dr. Nadeu said, smoke from recent Massachusetts wildfires isn’t helping.
“And so because of that — the pollution plus these allergens — both are heavy hitters in terms of increasing people’s lung and airway disease.”
Banerjee recommends people stay indoors when possible while allergen counts are high, and take allergy medication.
“We often will tell our patients in the spring season to really think about Saint Patrick’s Day ... to start the medications,” Banerjee said. “But the same thing in the fall. Don’t stop your medications prematurely as the cold is starting. But [instead] really [stop using medications at] the first frost and a sustained level of cold, which brings the environmental allergens down.”
