A Tree Bumblebee (Bombus hyporum) collecting pollen in my garden

Pollen, allergy causative agent

Source: https://www.niehs.nih.gov/health/topics/agents/allergens/pollen/index.cfm

To a tree or a flowering plant, pollen is necessary for life. But to millions of Americans (https://www.cdc.gov/nchs/fastats/allergies.htm) , 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.

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.


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

  • 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.
  • 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.
  • 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.
  • 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

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

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