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NIH MedlinePlus the Magazine, Trusted Health Information from the National Institutes of Health

Managing Allergies

A Pollen Primer

A plant

Several types of pollen cause mild to severe seasonal respiratory allergy, including allergic rhinitis and asthma. But helpful defenses are available, according to researchers at the National Institute of Environmental Health Sciences (NIEHS).

Plant Pollen

Ragweed and other weeds, such as curly dock, lambs quarters, pigweed, plantain, sheep sorrel, and sagebrush are prolific producers of pollen allergens. Ragweed season runs from August to November, but pollen levels usually peak by mid-September in many areas in the country. Pollen counts are highest in the morning, and on dry, hot, windy days.

Protecting yourself

  • Between 5:00 and10:00 in the morning, stay indoors. 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. Keep cool with air conditioners. Don’t use window or attic fans.
  • Use a dryer, not a line outside; dry your clothes and avoid collecting pollen on them.

Grass Pollen

Grass pollens are regional as well as seasonal. Their levels also are affected by temperature, time of day, and rain. Only a small percentage of North America’s 1,200 grass species cause allergies, including:

  • Bermuda grass
  • Johnson grass
  • Kentucky bluegrass
  • Sweet vernal grass
  • Timothy grass
  • Orchard grass

Protecting yourself

  • Have someone else mow your lawn. If you mow, wear a mask.
  • Keep grass short.
  • Grow ground covers that don’t produce much pollen, such as moss.
  • Treat respiratory allergy with antihistamines, topical nasal steroids, cromolyn sodium, decongestants, or immunotherapy (see page 20 for details).
  • Use an air purifier with high efficiency air filters (HEPA) or an electrostatic air filter.
Tree leaves

Tree Pollen

Trees produce pollen earliest, as soon as January in the south, and as late as May and June in the northeast. They release huge amounts that can be distributed miles away. Fewer than 100 kinds of trees cause allergies. Some common ones are catalpa, elm, hickory, sycamore, and walnut.

Protecting yourself

Plant species that do not aggravate allergies, such as crape myrtle, dogwood, fig, fir, palm, pear, plum, redbud, and redwood trees, or the female cultivars of ash, box elder, cottonwood, maple, palm, poplar, or willow trees.


Summer 2011 Issue: Volume 6 Number 2 Page 19