Whether they know it or not, most hay fever sufferers in North
America have Ragweed to thank for their autumnal misery. Ragweed
releases its vile pollen for six to eight weeks every year, starting
in mid-August and continuing through November in some areas. In
most areas, ragweed pollen levels peak in mid-September. During that period of time, a single ragweed plant is capable of producing over a billion grains of pollen. It is estimated that ragweed produces 100 million tons of pollen every year in the United
States.
Most ragweed species are native to North America, where they are most
prevalent in the midwest and central United States. There are few
places known to be ragweed-free in the United States, although Portland,
OR and Seattle, WA sometimes claim to have no
ragweed season. Cities with very mild ragweed seasons include Salt Lake City, UT and Bangor, ME.
Outside of North America, ragweed can also be found in Eastern Europe
and in the French Rhône valley.
Ragweeds are annuals with rough, hairy stems and mostly lobed or
divided leaves. Their flowers are greenish and inconspicuous. Since
ragweed is an annual, it can be eradicated simply by mowing it down
before it gets a chance to release its pollen. A member of the
Aster family, it grows mostly in disturbed vacant soils which cannot
support other vegetation. It flourishes during hot, dry weather.
There are several species of ragweed, but most ragweed allergies are
caused by two species which are present in nearly every region of the
United States: Ambrosia artemisiifolia (common
ragweed, which gets to be, at most, 5 feet tall) and Ambrosia
trifida (also known as giant ragweed because it can grow
to be 15 feet tall).
Fruits such as honeydew, cantaloupe, watermelon and banana
contain proteins which are similar enough to the offending bits of
ragweed pollen that they can produce reactions in allergic
individuals. To avoid compounding your symptoms, its best to avoid
these fruits. They can cause oral allergy syndrome, which is
itching or swelling of the lips, tongue, throat or roof of the mouth.
Chamomile, marsh elder, and mugwort may also cause problems for
those allergic to ragweed.
To reduce your exposure to ragweed pollen, it is best to stay indoors
between 5 and 10 AM, and also on dry, hot, windy days. The best time
to be outside is in the late afternoon or after a heavy rain, because
pollen levels are lower during these times. Keep your house and car
windows closed as much as possible.
After being outdoors, it is best to shower and change your
clothing. Pollen can adhere to clothing, skin, and hair. Be aware that
your pet can also transport pollen into your home. Wash your hands
after petting them, and resist the temptation to bury your face in their fur.
Sources:
allergies.about.com/cs/ragweed
pollen.utulsa.edu/ragweed.htm
www.auburn.edu/~deancar/wfnotes/ragwd.htm
www.niehs.nih.gov/airborne/prevent/ragweed.html
www.ppws.vt.edu/scott/weed_id/ambel.htm
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