Pollen

*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.