Indoor Allergens (cont.)
What are dust mites?
Dust mites, which were discovered in 1964, are microscopic arachnids (resembling tiny spiders). They are about
1/3 mm in length and are not visible to the naked eye. They have eight legs, are blind, and naturally live indoors. Their presence does not indicate that the house is dirty. This is because usual cleaning procedures, such as vacuuming and dusting, do not eliminate them.
Dust mites have "sticky" pads at the ends of their legs that help them to firmly attach to fibers, which allows them to live deep within carpeting, upholstery, and mattresses. Most of the mites found in houses are from the Dermatophagoides family, with pteronyssinus and farinae being the most common species. (Dermatophagoides comes from Latin and means skin-eating.
Pteronyssinus comes from Latin and means feather-loving. Farinae is Latin for flour.) Fortunately, dust mites do not bite, spread disease, or actually live on humans.
What conditions are most favorable to dust mites?
Dust mites thrive in warm, humid places. The ideal temperature for dust mites
ranges from 65 to 80 degrees F, a common range for indoor room temperatures.
Since dust mites have no means of drinking, they are totally dependent on the
humidity surrounding them for water. They live best at a relative humidity above
55%. However, also be aware that monitoring the humidity really isn't sufficient
to control dust mites. As the humidity falls, dust mites will retreat from the
surface. However, even in very dry conditions, it can take quite a few months to
eliminate the dust-mite population.
Dust mites derive their food supply from human secretions and the skin cells we
shed. (The average human sheds up to 1.5 grams of skin particles per day. A gram
is about the weight of a paper clip.) The mites thrive in articles such as
feather pillows and stuffed animals that collect sloughed skin cells and
secretions. The most favorable conditions for dust mite growth are found in the
bedroom. Their favorite breeding grounds are mattresses, pillows, and box
springs, as well as blankets, curtains, carpeting, and other fabric items in the
room.
The perfect climatic conditions for dust mites occur in North America in the mid-
and southern Atlantic coast, Gulf Coast, central Midwest, Pacific Northwest, and
British Columbia. Dust mites are rarely found in dry climates where the
elevation is over 5,000 feet above sea level.
Next: How do dust mites cause allergic symptoms? »
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