If your allergies feel worse this year than they did a decade ago, you are not imagining it. New Hampshire physicians say the state’s allergy season is getting longer, the overlap between different pollen types is increasing, and warmer, more humid conditions are amplifying the effect that allergens have on the respiratory system. The trend, driven in part by climate change and in part by the seasonal chemistry of the Granite State’s air, is affecting hundreds of thousands of residents each spring and summer.
As NHPR reported, two specialists with deep experience treating allergy and lung conditions in New Hampshire recently laid out both the causes and the practical steps residents can take to manage their symptoms during what has become an increasingly demanding season.
Why NH’s Allergy Season Keeps Getting Worse
The core of the problem is temperature and timing. Climate change is producing milder winters in New Hampshire, and milder winters mean shorter frost periods. Trees, grasses, and other plants use frost as a seasonal cue for dormancy. When frosts are shorter and lighter, plants begin pollinating earlier in the spring and continue later into the fall.
An Huynh, an allergist at Dartmouth Health, explained the chain reaction. “With shortening frost, trees will start to pollinate a little bit earlier,” Huynh said. That might sound like a minor shift, but it cascades through the entire pollen calendar in ways that make the total burden on allergy sufferers significantly heavier.
In New Hampshire, the pollen calendar typically begins with tree pollens in late March and April, as birch, maple, oak, and other hardwoods release large quantities of pollen into the air. Grass pollen follows through May, June, and into July. Weed pollens, most notably ragweed, dominate August and September. When the warm season extends in either direction, all three phases push further into the calendar, and the transitional periods where multiple pollen types are airborne simultaneously become longer and more intense.
Huynh said he is seeing more patients report intensified symptoms precisely because they are being exposed to multiple allergens at once. “There’s also more overlap in seasons,” he said, which compounds the body’s immune response and can make symptoms that would ordinarily be manageable feel overwhelming.
Heat, Humidity, and the Respiratory System
Beyond the timing of pollen release, the physical properties of New Hampshire’s summer air add another layer of complexity. Dr. Muhammad Mirza, a pulmonologist with Elliot Hospital, described how heat and humidity interact with airborne particles to make respiratory symptoms worse.
Heat increases pollutant concentrations in the lower atmosphere. Automobile emissions, particulate matter from road dust and construction, and, increasingly, smoke from wildfires combine with high temperatures to create air that is measurably more irritating to the upper and lower airways. For people with pre-existing conditions like asthma or chronic obstructive pulmonary disease, these compound exposures can trigger episodes that require medical attention.
“New Hampshire can get those windy days that can have an effect on extending and prolonging the allergen exposure because they stick around in the air longer,” Mirza said. The same wind patterns that Granite Staters associate with crisp, pleasant spring days can actually be among the worst conditions for allergy sufferers, because they keep pollen suspended in the air rather than allowing it to settle.
Humidity creates its own paradox. Low humidity causes the body’s mucous membranes to dry out, which triggers overproduction of mucus as a compensatory mechanism. High humidity, on the other hand, makes it harder to breathe and contributes to congestion. During a New Hampshire summer, residents can experience both conditions within the same week, or even the same day, as weather systems move through the region.
The Wildfire Factor
There is another factor that has become increasingly relevant to New Hampshire air quality in recent years: wildfire smoke. While New Hampshire itself does not have a large wildfire problem, prevailing wind patterns mean that smoke from fires in Canada and the American West regularly reaches the Northeast during summer months. That smoke carries fine particulate matter that irritates the respiratory system and can significantly worsen allergy and asthma symptoms even in people who do not normally have severe reactions.
New Hampshire has already seen the effects of this phenomenon firsthand. The province-wide Canadian wildfires in recent years sent visible haze across the Granite State on multiple occasions, and air quality advisories have become a more common feature of New Hampshire summers than they were a generation ago. For residents with allergies or lung conditions, a day with an air quality advisory on top of a high pollen count can be genuinely dangerous. The connection between climate-driven fire risk and air quality in the region is a topic that environmental and forestry researchers have been tracking closely as conditions change.
Practical Steps for NH Residents
Both Mirza and Huynh offered concrete advice for managing symptoms during the increasingly intense allergy seasons New Hampshire is experiencing.
The most consistent recommendation from both physicians is monitoring air quality data before spending extended time outdoors. Most major weather apps now include an Air Quality Index rating alongside temperature and precipitation forecasts. The AQI measures concentrations of major air pollutants on a scale from 0 to 500, with values below 50 considered good and values above 100 potentially problematic for sensitive groups. On days with both high pollen counts and elevated AQI readings, people with asthma or significant allergies should consider limiting outdoor activity or taking precautions.
For people with seasonal allergies, Mirza sometimes recommends starting antihistamines before pollen season peaks rather than waiting until symptoms develop. “Depending on the severity of their symptoms,” he said, preemptive treatment can prevent the immune cascade from becoming established, which makes it harder to control. This approach requires knowing your personal pollen calendar, which for most New Hampshire residents means tree pollen in spring, grass in early summer, and ragweed in late summer and fall.
Clothing and personal hygiene routines matter more during high-pollen periods than most people realize. Pollen clings to hair, fabric, and skin, and it can accumulate on a person’s body throughout a day spent outdoors. Mirza recommends changing clothes after spending time outside and taking more frequent showers during peak pollen periods. “If you’re sleeping with the pollen in your hair or your clothes throughout the night, you may be inhaling it and you may exacerbate symptoms the next day,” he said.
The Hidden Indoor Allergen
Huynh raised another issue that tends to be overlooked in discussions of seasonal allergies: dust mites. These microscopic organisms feed on dead skin cells and thrive in the warm, humid conditions that characterize New Hampshire summers. They colonize fabrics, and bedding is their preferred habitat.
“Our bed sheets are a really common place that we can find dust mites,” Huynh said. “When you’re sleeping underneath the covers and you produce your own local microclimate of humidity from your own body heat, that’s one of the big places that they can thrive.”
Dust mite populations peak during the summer months when household humidity is highest, which means that even residents who stay indoors on high-pollen days may be exposing themselves to a significant allergen source in their own bedrooms. Washing bedding in hot water weekly, using allergen-impermeable mattress and pillow covers, and running a dehumidifier to keep indoor humidity below 50 percent are all strategies that can reduce dust mite populations.
Managing a Changing Season
The broader picture that emerges from the advice of both physicians is that New Hampshire’s allergy season now requires a more proactive and year-round approach than it did for previous generations of Granite Staters.
For context on how other environmental pressures are reshaping daily life in the Granite State, NH Sea Grant coastal researchers are studying PFAS and flooding impacts that compound environmental health burdens.
The old model of allergy management, take some antihistamines when things get bad in May, was designed for a pollen season that ran roughly from April through October and peaked in May and August. The new reality is a season that starts earlier, ends later, overlaps more often, and compounds with outdoor air quality events that were rare a generation ago.
That change has particular implications for people with asthma. Asthma affects roughly 8 to 9 percent of adults in New Hampshire, a rate consistent with national averages. For those individuals, the combination of earlier tree pollen, longer grass pollen seasons, wildfire smoke events, and summer heat and humidity creates an increasingly challenging environment. Mirza and other pulmonologists consistently recommend that asthma patients maintain open communication with their care providers about how their symptoms are tracking and whether medication regimens need adjustment.
The underlying cause of this trend connects to the same climate dynamics that are reshaping other aspects of New Hampshire’s environment and economy. A warmer, longer growing season is good for agriculture and the state’s foliage tourism industry, but it carries real costs in terms of public health. New Hampshire’s forests, which attract millions of visitors and support a significant portion of the state’s identity and economy, are themselves changing under these conditions.
For residents dealing with allergy symptoms this spring and summer, the advice from Granite State physicians is straightforward: monitor the air quality index, start treatments before the season peaks if your symptoms are significant, shower and change clothes after time outdoors, and do not overlook the indoor environment as a source of allergen exposure. The season may be getting longer, but its impacts are manageable with the right preparation.
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