What are dust mites?
House dust mites are microscope bugs that primarily live on dead skin cells regularly shed from humans and their animal pets. Dust mites are generally harmless to most people. They don't carry diseases, but they can cause allergic reactions in asthmatics and others who are allergic to their feces. People sometimes confuse dustmites with bed bugs.
Skin cells and scales, commonly called dander, are often concentrated in lounging areas, mattresses, frequently used furniture and associated carpeted areas, often harbor large numbers of these microscopic mites. Since the average human sloughs off 1/3 ounce (10 grams) of dead skin a week. That gives dust mites a lot to eat. Cats and dogs create far more dander for dust mites to eat.
A typical mattress can contain tens of thousands of dust mites. Sick yet? Nearly 100,000 mites can live in one square yard of carpet. Ready to convince your spouse to start bathing regularly? Did you know a single dust mite produces about 20 waste droppings each day, each containing a protein to which many people are allergic. Yuck! The proteins in that combination of feces and shed skin are what cause allergic reactions in humans. Depending on the person and exposure, reactions can range from itchy eyes to asthma attacks. And finally, unlike other types of mites, house dust mites are not parasites, since they only eat dead tissue. Gross, but true.
Where do they live?
Beds are a prime habitat (where 1/3 of life occurs). A typical used mattress may have anywhere from 100,000 to 10 million mites inside. (Ten percent of the weight of a two year old pillow can be composed of dead mites and their droppings.) Mites prefer warm, moist surroundings such as the inside of a mattress when someone is on it. A favorite food is dander (both human and animal skin flakes). Humans shed about 1/5 ounce of dander (dead skin) each week. About 80 percent of the material seen floating in a sunbeam is actually skin flakes. Also, bedroom carpeting and household upholstery support high mite populations.
The University of Manchester performed a 2005 medical study of pillows that found up to 16 species of fungi in a single pillow. They tested feather and synthetic pillows in a range of ages, finding thousands of spores of fungus per gram of pillow ; more than is found on an average used toothbrush.
And just when you thought they were confined to your home and bedroom, there is a news story in USA Today in which Jill Holdsworth is an infection preventionist and president of the DC Metro Chapter of the Association for Professionals in Infection Control and Epidemiology says the car can be another place where dust mites live and a very big place to pass bacteria back and forth if you are not careful, saying "The No. 1 hot spots would be anywhere that you touch with your hands," Holdsworth said. These areas include the steering wheel, radio, gear shift, cup holders and car seats."
Biology and Life Cycle
Adult females lay up to 40 to 80 eggs singly or in small groups of three to five. After eggs hatch, a six-legged larva emerges. After the first molt, an eight-legged nymph appears. After two nymphal stages occur, an eight-legged adult emerges. The life cycle from egg to adult is about one month with the adult living an additional one to three months.
The diet is varied with the primary food source, consisting of dander (skin scales) from humans and animals. However, needed nutrients can be provided from fish food flakes, pet food, fungi, cereals, crumbs, etc. Many mite species live in bird's nests, in barns, among stored grain, straw, etc.
House dust mites are cosmopolitan in distribution with much of the research previously done in Europe.
One of the major limiting factors in mite survival and population development is the availability of water for sorption. Highest mite densities occur in the humid summer months and lowest in drier winter periods. Dust mite populations are highest in humid regions and lowest in areas of high altitude and/or dry climates.
(source: Environment, Health and Safety Online)