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Triggers Seasonal Allergic Rhinitis

After a long winter this phrase is a welcome relief from the dark winter chill. However, if you are one of the 35 million Americans with spring allergies this can be a season of congestion, itching and miserable allergies.

Seasonal allergic rhinitis, often referred to as "hay fever" is triggered by a common allergen called pollen.

Each spring, tiny pollen grains are released from trees and grasses and carried on currents of air. Many trees and grasses have small, light dry pollens that are easily picked up and carried by the wind. When they enter the nose, throat or eyes of the allergy sufferer they cause irritating symptoms of seasonal allergic rhinitis.

What is pollen?

Plants produce microscopic round grains called pollen in order to reproduce. Some plants use their own pollen to fertilize themselves. Other plants send the pollen from one plant to another with the help of insects or the wind. This is called cross-pollination.

The plain-looking plants such as trees and grass produce types of pollen that cause most allergic reactions. These plants manufacture small, light dry pollen granules that are easily transported in the wind and can drift for many miles.

Pollens from plants with bright colors, such as roses or garden flowers, usually do not cause allergic symptoms. We commonly hear people say they are allergic to colorful or scented flowers; but these large pollens carried by insects, such as bees and butterflies, are too heavy to be blown about by wind and, thus, do not have the opportunity to enter our noses or airways.

Most allergic pollen comes from plants that produce it in large quantities. Some plants can generate a million grains of pollen a day.

The chemical nature of a pollen also determines whether it will be allergic or not. For example, pine pollen is produced in large quantities by a very common tree, which would make it a good candidate for causing allergy. However, the chemical composition of pine pollen makes it less allergic than other types of pollen. In addition, pine pollen is very heavy and tends to fall more rapidly to the ground rarely reaching the human nose. It is the yellow dust we see each spring on our cars and porches, but it is not the cause of many symptoms. Other trees pollinate at the same time and have small, invisible pollens that float easily in the air. These pollens are the source of the allergic symptoms, but it is the yellow pine pollen that captures all the blame!

Each plant has a pollinating season that is more or less during the same time each year. Exactly when a plant starts to pollinate seems to depend on the relative length of night and day; but during pollination, weather conditions can affect the amount of pollen produced and distributed. The "season" for trees is in the early spring and grasses in late spring and early summer. The farther north you go, the later the pollinating period and the later the allergy season.

A pollen count, heard quite often in the spring on local weather reports, is a measure of how much pollen is in the air. Pollen counts tend to be highest in early morning on warm, dry breezy days and lowest during colder, wet weather. The pollen count is useful as a general guide for when it may be wise to stay indoors and avoid contact with pollen.

Pollen Producing Grass

Some grasses that produce pollen:

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

Pollen Producing Trees

Some trees that produce pollen:

  • Oak
  • Ash
  • Hickory
  • Pecan
  • Boxelder
  • Mountain cedar
  • Elm

Signs and Symptoms of Pollen Allergy

  • Sneezing
  • Runny, congested nose
  • Itching eyes, nose, and throat
  • Allergic Shiners- dark circles under the eyes caused by restricted blood flow near the sinuses
  • Watering eyes

When the allergy causing pollen land on the mucous membranes of the nose of an allergic person, certain chemicals are released from the cells that cause nasal passages to swell producing itching, irritation and excess mucous. Some people with a pollen allergy think they have a spring or summer cold. When the symptoms continue for weeks, it is important to see your doctor and rule out the possibility of allergy.

Contact Information

Allergy and Inflammation - Research
Department of Medicine
Beth Israel Deaconess Medical Center
Center for Life Science, 9th floor
330 Brookline Avenue
Boston, MA 02215