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Pollens
Tue May 25, 2004
Listen in RealAudio 
Aaachoo! Dear me, is it hay-fever season again? Hi, I'm Bryan Yeaton for The Weather
Notebook.
The term hay fever arose several centuries ago when many people who lived and
worked on farms felt ill during haying time. They sneezed terribly; their noses ran; their
eyes itched and swelled. Most were convinced the hay, or perhaps the hot weather,
had made them sick. Finally in 1873, Englishman Charles Blackley associated the
condition with plant pollens.
Hay fever is not really a fever since sufferers don't run a temperature. It's also
misleading because hay has little to do with it. Technically, these warm-weather
allergies are called allergic rhinitis, which means "inflammation of the nose".
Hay fever arises in early summer with the maturing of grasses. It continues from early
August until the first hard freeze, compliments of many weed species, particularly
ragweed, to which 75 percent of hay-fever sufferers are sensitive. Cross-reactivity
among these pollens ensures that a reaction to one will almost certainly cause
reactions to all.
These weeds produce copious amounts of pollen designed to be dispersed by the
wind. The warm, dry, breezy days common in late summer and early fall provide
optimal weather for pollen to be spread over wide areas, as the little devils rise high on
ascending air currents. Pollen counts vary during the day as the diurnal weather cycle
unfolds in concert with pollen production.
Rain usually relieves allergy symptoms because it literally washes pollens out of the
air. But for allergy sufferers, the real relief comes with the cold temperatures, as old
Jack Frost closes the pollen factories for another year.
Thanks to our contributing writer, meteorologist Keith Heidorn. Our show is produced
by the Mount Washington Observatory, and underwritten by the National Science
Foundation, and Subaru of America.
Today's Links
Aeroallergens: Misery Blowin\' In The Wind
http://www.islandnet.com/~see/weather/almanac/arc2001/alm01aug.htm
Aerobiology Research Laboratories: Pollen Allergen
http://www.pollenplus.com/pollen/index.html
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