Apply flea and tick powders outdoors. And try to apply pesticides only when and where pests are present. Researchers now believe that it is principally the feces of dust mites that trigger allergies. The dander, saliva, and urine of pets also contain allergens, as do cockroaches. And there is some evidence that dust mite or cockroach allergens work in concert with air pollutants such as ozone and particulate matter to exacerbate asthma, says Patrick Breysse, an environmental health scientist at Public Health, who is investigating that theory.
Biological invaders can even occasionally prove fatal.
The infamous Legionella bacterium can contaminate building cooling systems, get blown into room air, and become inhaled, leading to the potentially fatal illness known as Legionnaire's disease. To cut down on dust and allergens in the home, cover mattresses and pillows with impermeable liners and wash bedclothing once a week in water that is at least 140 degrees Fahrenheit. Mop floors and furniture with a damp mop or rag, and vacuum regularly, using a double-layered microfilter bag or HEPA filter. Choose washable curtains or shades. Keep relative humidity below 50 percent, through use of a dehumidifier or air conditioner, and make sure that air conditioners have proper drainage.