*What is pollen?
Plants produce microscopic round or oval pollen grains to
reproduce. In some species, the plant uses the pollen from
its own flowers to fertilize itself.
Other types must be cross-pollinated; that is, in order for
fertilization to take place and seeds to form, pollen must
be transferred from the flower of one plant to that of
another plant of the same species. Insects do this job for
certain flowering plants, while other plants rely on wind
transport.
The types of pollen that most commonly cause allergic re-
actions are produced by the plain-looking plants (trees,
grasses, and weeds) that do not have showy flowers. These
plants manufacture small, light, dry pollen granules that
are custom-made for wind transport.
Samples of ragweed pollen have been collected 400 miles out
at sea and two miles high in the air. Because airborne
pollen is carried for long distances, it does little good
to rid an area of an offending plant--the pollen can drift
in from many miles away. In addition, most allergenic pollen
comes from plants that produce it in huge quantities. A
single ragweed plant can generate a million grains of pollen
a day.
The chemical makeup of pollen is the basic factor that
determines whether it is likely to cause hay fever. For
example, pine tree pollen is produced in large amounts by
a common tree, which would make it a good candidate for
causing allergy. The chemical composition of pine pollen,
however, appears to make it less allergenic than other
types. Because pine pollen is heavy, it tends to fall
straight down and does not scatter. Therefore, it rarely
reaches human noses.
Grasses and trees, too, are important sources of allergenic
pollens. Although more than 1,000 species of grass grow in
North America, only a few produce highly allergenic pollen.
These include timothy grass, Kentucky bluegrass, Johnson
grass, Bermuda grass, redtop grass, orchard grass, and sweet
vernal grass. Trees that produce allergenic pollen include
oak, ash, elm, hickory, pecan, box elder, and mountain cedar.
*When do plants make pollen?
One of the most obvious features of pollen allergy is its
seasonal nature--people experience it symptoms only when
the pollen grains to which they are allergic are in the
air. Each plant has a pollinating period that is more or
less the same from year to year.
Exactly when a plant starts to pollinate seems to depend
on the relative length of night and day--and therefore on
geographical location--rather than on the weather.
On the other hand, weather conditions during pollination
can affect the amount of pollen produced and distributed
in a specific year. Thus, the farther north you go, the
later the pollinating period and the later the allergy
season.
Generally tree, grass, and weed seasons are similar every
year in the same location. However, the intensity can differ
depending on the current weather, the previous year's
weather, and other environmental factors. Typically, trees
pollinate earliest from February to May, grasses follow in
May to mid-July, and weeds peak from late summer to early
fall.
A pollen count, which is familiar to many people from local
weather reports, is a measure of how much pollen is in the
air. This count represents the concentration of all the
pollen (or of one particular type, like ragweed) in the air
in a certain area at a specific time. It is expressed in
grains of pollen per square meter of air collected over 24
hours.
Pollen counts tend to be highest early in the morning on
warm, dry, breezy days and lowest during chilly, wet periods.
Although a pollen count is an approximate and fluctuating
measure, it is useful as a general guide for when it is
advisable to stay indoors and avoid contact with the pollen.
*Why do pollen and mold counts vary so much from day to day?
Changes in temperature, wind conditions, humidity, or precip-
itation can affect the counts greatly.
*Temperature: A sudden temperature drop lowers the pollen
count significantly. Certain pollens are seasonal. Trees are
dominant in the spring, grasses occur in late spring and
early summer, and weeds grow from late summer until the first
hard frost.
*Wind: Pollens are small, light, and dry so they are easily
spread by wind. The distance the pollen travel can depend on
whether the wind is strong or calm that day.
*Humidity: When the air is humid, pollen becomes damp and
heavy with moisture keeping it still and on the ground.
*Precipitation: Rains tend to "cleanse" the air of pollen.
When the pollen is wet, it becomes heavy with moisture
keeping it on the ground.
*During the peak of the pollen or mold season that affects
you, try following these guidelines:
Keep windows closed at night.D
Minimize early morning outdoor activity when most pollen is
released (between 5-10 AM).
Keep your car windows closed when traveling.
Stay indoors when the pollen count is high and on windy days
when dust and pollen are easily scattered.
Vacation during the peak of pollen season to an area where
there is less pollen, like the beach.
Take any medications your allergist recommends as prescribed.
Do not rake leaves, mow lawns, or be around freshly cut
grass. This stirs up pollen and mold.
Do not hang laundry outside to dry. Pollen and mold will
collect in them.
Keep indoor plants to a minimum and never overwater if
allergic to mold. Wet soil encourages mold growth.
POLLEN TRIVIA
One recent study found that children who have fevers (of 101
degrees Fahrenheit) before they reach the age of one tend to
have a lower likelihood of developing allergies by age seven.
It's just as bad for our dogs and cats, especially those with
allergies, as it is for humans.
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