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Your Environment. Your Health.

Pollen

Introduction

sneezing boy standing in wildflowers

To a tree or a flowering plant, pollen is necessary for life. But to millions of Americans, it is a source of seasonal misery.

Pollen, a fine to coarse powdery substance, is created by certain plants as part of their reproduction process. It can appear from trees in the spring, grasses in the summer, and weeds in the fall.

Pollen in the air can trigger sneezing, congestion, watery eyes, and other cold-like symptoms. Seasonal allergies – also known as allergic rhinitis or hay fever – may affect nearly one in six Americans.1

Research suggests that weather changes can affect allergy symptoms. Extreme weather events, such as heat waves and thunderstorms, have been associated with outbreaks of allergic asthma, especially in patients suffering from pollen allergy.2

Visit the Join an NIEHS Study Website

Join an asthma study!

The goal of the Natural History of Asthma with Longitudinal Environmental Sampling (NHALES) study is to help scientists understand how bacteria and other factors in the environment affect people who have moderate to severe asthma.

Who can participate?

  • Moderate to severe asthmatics.
  • Males and females, aged 18-60.
  • Females should not be pregnant or breastfeeding at the start of the study, but may still participate if they become pregnant during the study.
  • Nonsmokers who are also not around significant amounts of secondhand smoke.
  • No history of chronic obstructive pulmonary disease, emphysema, cystic fibrosis (CF), pulmonary fibrosis, non-CF bronchiectasis, sarcoidosis, unstable angina, or pulmonary hypertension.
  • Not allergic to methacholine.
  • Able to provide your own transportation to clinic visits on the NIEHS campus in North Carolina.

    For more information about this study:
    NHALES: Asthma Study
    Tel 855-MYNIEHS (855-696-4347)
    nhales@mail.nih.gov

FDA-approved allergy treatments are available for children and adults. Common antihistamines and nasal steroid sprays can reduce hay fever symptoms. Scientists are also trying to design nasal filters that can screen out pollen without getting in the way of natural breathing.3

What is NIEHS Doing?

In recent years, NIEHS-funded studies have explored the effects of a changing climate on the production of pollen.

  • Higher pollen counts – Changes in climate may result in higher pollen counts. The annual average of daily airborne pollen amounts increased 46% between 1994-2000 and 2001-2010.4
  • Longer pollen season – A warming climate lengthened the pollen season by as much as 13 to 27 days in the northern United States between 1995 and 2009.5
  • More hay fever – Nationally representative data from the National Health Interview Survey indicated that exposure to extreme heat events is associated with increased prevalence of hay fever in U.S. adults.6
  • Increased health care usage – Higher pollen counts are related to allergy and asthma symptoms, as measured by over-the-counter allergy medication use and emergency-department and physician-office visits for allergic disease.7

Further Reading

Stories from the Environmental Factor (NIEHS Newsletter)

Stories from Environmental Health Perspectives (EHP)

pollen written on a car

Additional Resources

For more information on pollen:
800-9-POLLEN or 800-976-5536

Related Health Topics

Research Links

For Educators

  • Allergy Prevention Strategies
    • Avoid the outdoors between 5:00 - 10:00 a.m. Save outside activities for late afternoon or after a heavy rain, when pollen levels are lower.
    • Keep windows in your home and car closed to lower exposure to pollen. To keep cool, use air conditioners and avoid using window and attic fans.
    • Be aware that pollen can be transported indoors on people and pets.
  • Ragweed Pollen
    Ragweed and weeds such as curly dock, lamb’s quarters, pigweed, plantain, sheep sorrel and sagebrush are among the most prolific producers of pollen. The ragweed pollen season runs from August to November, with pollen levels typically peaking mid-September in many areas in the country.
  • Grass Pollen
    Grass pollen types are regional as well as seasonal. Grass pollen levels can be affected by temperature, time of day, and rain. The best way to avoid grass pollens is to wear a mask when mowing your lawn or ask someone else to mow it. Be sure to keep grass cut short or consider an alternative ground cover that doesn't produce much pollen, such as Irish moss, bunch, and dichondra.

    More than 1000 species of grass grow in North America, but only a few cause allergies. The most common species associated with allergies are:
    • Bermuda grass
    • Johnson grass
    • Kentucky bluegrass
    • Orchard grass
    • Sweet vernal grass
    • Timothy grass

  • Tree Pollen
    Trees release their pollen as early as January in the Southern states and as late as May or June in the Northern states. Tree pollen can be distributed miles away from the original source. 

    When choosing trees for your yard, look for species that are less likely to cause allergic reactions, such as:
    • Crape myrtle
    • Dogwood
    • Fig
    • Fir
    • Pear
    • Plum
    • Redbud
    • Redwood
    • Female cultivars of ash, box elder, cottonwood, maple, palm, poplar, or willow tree

    People with tree pollen allergies should avoid the following trees:
    • Catalpa
    • Elm
    • Hickory
    • Oak
    • Pecan
    • Sycamore
    • Walnut

  1. Seidman MD, Gurgel RK, Lin SY, Schwartz SR, Baroody FM, Bonner JR, Dawson DE, Dykewicz MS, Hackell JM, Han JK, Ishman SL, Krouse HJ, Malekzadeh S, Mims JW, Omole FS, Reddy WD, Wallace DV, Walsh SA, Warren BE, Wilson MN, Nnacheta LC, 2015. Clinical practice guideline: Allergic rhinitis. Otolaryngology–Head and Neck Surgery 152(1 Suppl):S1-43. [Abstract Seidman MD, Gurgel RK, Lin SY, Schwartz SR, Baroody FM, Bonner JR, Dawson DE, Dykewicz MS, Hackell JM, Han JK, Ishman SL, Krouse HJ, Malekzadeh S, Mims JW, Omole FS, Reddy WD, Wallace DV, Walsh SA, Warren BE, Wilson MN, Nnacheta LC, 2015. Clinical practice guideline: Allergic rhinitis. Otolaryngology–Head and Neck Surgery 152(1 Suppl):S1-43.]
  2. D’Amato G, Cecchi L, Annesi-Maesano I, 2012. A Trans-disciplinary overview of case reports of thunderstorm-related asthma outbreaks and relapse. Eur Respir Rev 21(124): 82-87. [Abstract D’Amato G, Cecchi L, Annesi-Maesano I, 2012. A Trans-disciplinary overview of case reports of thunderstorm-related asthma outbreaks and relapse. Eur Respir Rev 21(124): 82-87.]
  3. Kenney P, Hilberg O, Laursen AC, Peel RG, Sigsgaard T. 2015. Preventive effect of nasal filters on allergic rhinitis: A randomized, double-blind, placebo-controlled crossover park study. J Allergy Clin Immunol 136(6):1566-1572.e1-5. [Abstract Kenney P, Hilberg O, Laursen AC, Peel RG, Sigsgaard T. 2015. Preventive effect of nasal filters on allergic rhinitis: A randomized, double-blind, placebo-controlled crossover park study. J Allergy Clin Immunol 136(6):1566-1572.e1-5.]
  4. Zhang Y, Bielory L, Mi Z, Cai T, Robock A, and Georgopoulos P. 2015. Allergenic pollen season variations in the past two decades under changing climate in the United States. Glob Chang Biol 21(4):1581-1589. [Abstract Zhang Y, Bielory L, Mi Z, Cai T, Robock A, and Georgopoulos P. 2015. Allergenic pollen season variations in the past two decades under changing climate in the United States. Glob Chang Biol 21(4):1581-1589.]
  5. Ziska L, Knowlton K, Rogers C, Dalan D, Tierney N, Elder MA, Filley W, Shropshire J, Ford LB, Hedberg C, Fleetwood P, Hovanky KT, Kavanaugh T, Fulford G, Vrtis RF, Patz JA, Portnoy J, Coates F, Bielory L, Frenz D. 2011. Recent warming by latitude associated with increased length of ragweed pollen season in central North America. Proc Natl Acad Sci 108(10): 4248-4251. [Abstract Ziska L, Knowlton K, Rogers C, Dalan D, Tierney N, Elder MA, Filley W, Shropshire J, Ford LB, Hedberg C, Fleetwood P, Hovanky KT, Kavanaugh T, Fulford G, Vrtis RF, Patz JA, Portnoy J, Coates F, Bielory L, Frenz D. 2011. Recent warming by latitude associated with increased length of ragweed pollen season in central North America. Proc Natl Acad Sci 108(10): 4248-4251.]
  6. Upperman CR, Parker JD, Akinbami LJ, Jiang C, He X, Murtugudde R, Curriero FC, Ziska L, Sapkota A. 2017. Exposure to extreme heat events Is associated with increased hay fever prevalence among nationally representative sample of US adults: 1997-2013. J Allergy Clin immunol. In practice 5(2):435-441. [Abstract Upperman CR, Parker JD, Akinbami LJ, Jiang C, He X, Murtugudde R, Curriero FC, Ziska L, Sapkota A. 2017. Exposure to extreme heat events Is associated with increased hay fever prevalence among nationally representative sample of US adults: 1997-2013. J Allergy Clin immunol. In practice 5(2):435-441.]
  7. Ito K, Weinberger KR, Robinson GS, Sheffield PE, Lall R, Mathes R, Ross Z, Kinney PL, Matte TD. 2015. The associations between daily spring pollen counts, over-the-counter allergy medication sales, and asthma syndrome emergency department visits in New York City, 2002-2012. Environ Health 14: 71; doi: 10.1186/s12940-015-0057-0 [Online 27 August 2015) [Available Ito K, Weinberger KR, Robinson GS, Sheffield PE, Lall R, Mathes R, Ross Z, Kinney PL, Matte TD. 2015. The associations between daily spring pollen counts, over-the-counter allergy medication sales, and asthma syndrome emergency department visits in New York City, 2002-2012. Environ Health 14: 71; doi: 10.1186/s12940-015-0057-0 [Online 27 August 2015)]

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