106 Million Americans Face Worse Allergies: 2026 Study Reveals Climate Change Is Driving Longer Pollen Seasons

More than 106 million Americans are experiencing longer, more intense allergy seasons due to climate change, according to the 2026 Allergy Capitals report released by the Asthma and Allergy Foundation of America (AAFA). For the first time, Boise, Idaho has claimed the top spot as the most challenging city for pollen allergies, marking a dramatic shift from previous years when Southeastern cities dominated the rankings.

The report's findings point to climate change as the primary driver behind worsening allergy conditions across the United States, with extreme weather events creating perfect storm conditions for heightened pollen production and extended allergy seasons.

Boise, Idaho: A Shocking Rise From 95th to 1st Place

Boise's ascent to the number one Allergy Capital represents one of the most dramatic shifts in AAFA's reporting history. Just last year, Boise ranked 95th out of 100 cities, considered one of the better places for allergy sufferers. Today, it tops the list after experiencing extraordinarily heavy tree and grass pollen loads during spring 2025.

According to Hannah Jaffee, AAFA's Research Director, Boise's unprecedented jump was driven by multiple factors converging simultaneously. Tree pollen peaked earlier than usual, grass pollen started earlier and lasted longer with significantly more days of high counts, and weed pollen extended much deeper into fall with higher peaks. The city also suffers from a shortage of allergy specialists, with only 0.67 allergists per 100,000 people compared to the national average of 1.1 per 100,000.

Dr. Bill Palmer, an allergist who has practiced in Boise's Treasure Valley for over two decades, confirms what patients have been experiencing firsthand. "When I first started, we thought of grass pollen season here as mid-May through Fourth of July," Palmer explained. "And now it's much longer."

The 2026 Top 20 Allergy Capitals: A West Coast Phenomenon

The 2026 rankings reveal a notable geographic shift, with Western cities appearing in unprecedented numbers among the most challenging places for allergy sufferers:

1. Boise, ID
2. San Diego, CA
3. Tulsa, OK
4. Provo, UT
5. Rochester, NY
6. Wichita, KS
7. Raleigh, NC
8. Ogden, UT
9. Spokane, WA
10. Greenville, SC
11. San Francisco, CA
12. Minneapolis, MN
13. Salt Lake City, UT
14. Richmond, VA
15. Colorado Springs, CO
16. Little Rock, AR
17. Toledo, OH
18. New Orleans, LA
19. Winston-Salem, NC
20. Lakeland, FL

This westward shift reflects changing weather patterns driven by climate change, particularly affecting regions that previously enjoyed more moderate allergy seasons.

Three Climate Phenomena Fueling America's Allergy Crisis

The AAFA report identifies three specific weather phenomena that have significantly contributed to heightened pollen production in 2025:

Atmospheric Rivers

These powerful storm systems deliver extended periods of moisture that encourage plants to flower earlier and produce more abundant pollen. The increased moisture from storms in late 2024 had a direct measurable effect on pollen seasons across the Pacific Northwest and beyond. Research shows atmospheric rivers have intensified over the past 45 years, with climate change expected to make them even stronger and more frequent.

Warmer Temperatures

Elevated temperatures trigger plants to begin growth cycles sooner, resulting in earlier pollen onset and extended duration. In Boise, a warmer-than-average winter led to tree pollen appearing much earlier than typical, catching many allergy sufferers unprepared for season onset.

Drought Conditions

Paradoxically, drought stress can also stimulate certain plants to produce more pollen as they attempt to reproduce before environmental conditions become untenable. This mechanism contributed to higher pollen counts in regions experiencing dry spells despite limited moisture.

The Science Behind Climate Change and Pollen Production

Dr. Amin Kanani, clinical associate professor and head of the division of allergy and clinical immunology at the University of British Columbia, explains the biological mechanisms driving this trend. "Warmer temperatures and higher CO2 levels are leading to longer growing seasons and more plant growth, because plants use CO2 as their fuel to grow," Dr. Kanani states. "With more plants there's more pollen being produced—studies show that pollen seasons are becoming longer and peak pollen counts are getting higher."

Scientific literature supports these observations. A comprehensive analysis published in Nature Communications projected that climate-driven changes could shift the start of spring pollen emissions 10-40 days earlier by century's end, with summer and fall weed and grass seasons extending 5-15 days later. The study also estimated annual total pollen emissions could increase by 16-40% due to phenological changes and temperature-driven pollen production.

Research from Scientific Reports examining nearly 30 years of data (1995-2022) in Northern Italy found clear correlations between meteorological variables and pollen season features. The study documented an anticipated onset of pollen seasons linked to increasing temperature and solar radiation, with projections indicating potential advances of up to 2 weeks over the next 60 years for weed species specifically.

Pollen's Impact Beyond Sneezing: 106 Million Americans Affected

The consequences of longer, more intense pollen seasons extend far beyond simple discomfort. Pollen acts as a significant trigger for multiple health conditions affecting millions:

• Pollen Allergy: Exact numbers unknown but represents millions directly affected
• Seasonal Allergic Rhinitis (Hay Fever): 82 million Americans experience this pollen-triggered condition
• Asthma: 28 million Americans have asthma, with most cases being allergic asthma triggered by pollen exposure
• Allergic Conjunctivitis: 34-68 million people suffer from eye allergies
• Nasal Polyps: 2 million people affected
• Eczema: 30 million Americans experience this skin condition that can be exacerbated by allergen exposure
• Pollen Food Allergy Syndrome: Affects 10-20% of people with allergic rhinitis
• Eosinophilic Esophagitis (EoE): 485,000 Americans diagnosed

"For some people, allergies can be life-altering," Dr. Palmer emphasizes. "They just cannot function, they can't work, they can't play."

The economic and productivity impacts are substantial, with allergy symptoms causing missed school days for children and reduced work productivity for adults nationwide.

Understanding the Ranking Methodology

AAFA's Allergy Capitals report evaluates the 100 most populous metropolitan statistical areas in the contiguous United States using three weighted factors:

Pollen Scores: Assessment of tree, grass, and weed pollen counts, measuring how many days each city experiences high or very high pollen levels throughout the year.

Over-the-Counter Allergy Medicine Use: Analysis of prescription refill data and medication purchases indicating symptom severity and treatment needs in each region.

Availability of Board-Certified Allergists/Immunologists: Measurement of specialist access relative to population size, recognizing that adequate medical care availability affects overall management capability.

These factors are not weighted equally in the final scoring, with pollen counts typically carrying the most significant influence on rankings.

Three-Step Approach to Managing Pollen Allergies

Regardless of geographic location, Dr. Neeta Ogden, AAFA's medical spokesperson, emphasizes that effective symptom management is achievable through a comprehensive approach.

Step 1: Minimize Pollen Exposure

Reducing contact with pollen directly decreases symptom severity. Key strategies include:

• Daily monitoring of pollen counts and forecasts using apps like IQAir or pollen forecasting services
• Implementation of home allergen control measures including HEPA air purifiers
• Saline nasal rinses to clear accumulated pollen from nasal passages
• Showering before bedtime to remove pollen from skin and hair
• Keeping windows closed during peak pollen seasons
• Changing clothes after extended outdoor exposure

Step 2: Medication Management

Multiple treatment options exist for symptom control:

• Non-sedating oral antihistamines for systemic symptom relief
• Prescription nasal corticosteroid sprays for inflammatory symptoms
• Antihistamine eye drops for ocular allergy symptoms
• Leukotriene modifiers for asthma-associated allergic symptoms

Experts recommend initiating allergy medications 1-2 weeks before anticipated season onset for optimal effectiveness, rather than waiting for symptoms to develop.

Step 3: Immunotherapy Considerations

For patients who don't achieve complete relief with medications alone, allergists may recommend immune system-modifying treatments:

• Traditional subcutaneous immunotherapy (allergy shots) administered in clinical settings
• Sublingual immunotherapy tablets taken daily at home for specific pollen allergies
• Biologic medications that target specific components of the allergic response pathway

Dr. Kanani notes that long-term desensitization through immunotherapy "can significantly reduce reactivity to the pollen for many years," offering potentially lasting relief beyond temporary symptom management.

When Allergies Become Medical Emergencies

While most pollen allergies cause discomfort rather than danger, certain situations warrant urgent medical attention:

Asthma Exacerbations: People with asthma may experience worsening symptoms including wheezing, shortness of breath, and coughing during high pollen periods. Those with difficulty breathing should use rescue inhalers immediately and seek emergency care if symptoms don't improve quickly.

Anaphylaxis from Ingestion: Although uncommon with airborne exposure anaphylactic reactions can occur if pollen is ingested, such as when playing in grassy areas and pollen enters the mouth. Emergency treatment with epinephrine may be required.

Severe Reactions: Significant swelling affecting breathing or vision requires immediate emergency department evaluation.

The Role of CO2 in Intensifying Allergy Seasons

Beyond temperature effects, rising atmospheric carbon dioxide levels play a crucial role in worsening allergies through a process known as CO2 fertilization. Plants use carbon dioxide as fuel for growth through photosynthesis, meaning higher CO2 concentrations directly translate to increased plant biomass and pollen production.

Studies indicate that doubling atmospheric CO2 could significantly increase ragweed pollen production specifically—the culprit behind severe fall allergy symptoms for millions. This effect compounds with temperature-driven changes to create what climate scientists describe as a "perfect storm" for allergy sufferers.

Looking Forward: Projections Through 2080

Climate models predict these trends will intensify as global temperatures continue rising. Estimates suggest pollen seasons could extend by 15-55 days by the end of the century, with pollen production potentially increasing up to 200% in certain regions.

The implications for public health are substantial. Dr. Kenneth Mendez, AAFA President and CEO, framed the situation starkly: "We are experiencing a public health emergency fueled by climate change. Extreme weather events create the conditions for higher pollen levels and longer allergy seasons."

Kenneth Mendez emphasizes this represents more than individual discomfort—it's a widening health threat requiring urgent policy attention. "This report is a call to action for policymakers," Mendez states. "We need climate solutions, and we need them now."

Regional Variations: Not Everyone Affected Equally

While some regions face intensifying allergy conditions, others remain relatively spared due to geographic and climatic factors. The 10 least challenging cities for seasonal allergies in 2026 include Houston, New York City, San Antonio, Boston, Phoenix, Fresno, Harrisburg, El Paso, McAllen, and Tucson.

These areas benefit from various factors including lower native pollen-producing vegetation, different climate patterns that don't favor intense pollen production, or better access to allergy specialists relative to population.

Taking Action: Individual and Policy Solutions

At the individual level, proactive management remains essential regardless of geographic location. Consulting allergists for personalized treatment plans, monitoring pollen forecasts, and implementing environmental controls can significantly improve quality of life during allergy seasons.

On a broader scale, the AAFA report advocates for policy solutions addressing root causes. Recommendations include enforced emissions reduction laws, improved air quality standards, and investment in climate change mitigation strategies that will ultimately reduce the environmental drivers intensifying pollen production.

The intersection of climate policy and public health has never been more relevant as Americans face increasingly challenging allergy seasons driven by forces beyond individual control.

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References

1. Asthma and Allergy Foundation of America. (2026). 2026 Allergy Capitals Report. Retrieved from https://aafa.org/asthma-allergy-research/allergy-capitals/

2. Singh, A. B., & Kumar, P. (2022). Climate change and allergic diseases: An overview. Frontiers in Allergy, 3, 964987. https://doi.org/10.3389/falgy.2022.964987

3. Morgan, C. (2026, March 17). Boise tops US cities as worst for those with pollen allergies. Yahoo News. https://www.yahoo.com/news/articles/boise-tops-us-cities-worst-224810811.html

4. Goldhawk, B. (2026, March 26). Seasonal allergies are getting worse—and climate change is partly to blame. UBC News. https://news.ubc.ca/2026/03/seasonal-allergies-climate-change/

5. Bonini, M., Cardarelli, E., Faccini, M., et al. (2026). Effects of climate change on pollen season features of herbaceous species in the Milan area, Northern Italy. Scientific Reports, 16, 41641. https://doi.org/10.1038/s41598-026-41641-w

6. Anderegg, W. R. L., et al. (2021). Anthropogenic climate change is worsening North American pollen seasons. Proceedings of the National Academy of Sciences, 118, e2013284118. https://doi.org/10.1073/pnas.2013284118

7. Augustin, J., Gilge, S., Appel, H., et al. (2025). Climate Change, Air Quality, and Pollen Allergies—State of the Art and Recommendations for Research and Public Health. Allergy, 81(3), 663-683. https://doi.org/10.1111/all.70159

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Disclaimer: This article is for informational purposes only and does not constitute medical advice. Always consult with a qualified healthcare provider or allergist for diagnosis and treatment of allergy symptoms. If you experience severe allergic reactions or difficulty breathing, seek emergency medical care immediately.