The inventor of the microscope, van Leeuwenhoek, reported in 1694 that mites live in dust. Now, more than 300 years later, it is an established fact that dust mites can be found in house dust all over the world. There are two common dust mites, the American house dust mite and the European house dust mite. These dust mites are microscopic, less than 1/100th of an inch, and live in bedding, couches, carpet, stuffed toys, and old clothing. Dust mites feed on the dead skin that falls off the body of humans and animals and on other organic material found where they live.
Though these mites live in many homes, only people who are allergic to them know they are there. Dust mites are second only to pollen in causing allergic reactions. When dust mites grow, they shed their skin. The shed skin and feces are what cause allergic reactions in people. Allergic reactions range from itching noses and eyes to severe asthma attacks.
Dust mites do not live in air ducts in homes. Many people spend much time and money cleaning the air ducts to reduce dust mites. This is not necessary because dust mites need about 70% relative humidity or higher, and they need food. Areas where people spend much time, like in bed or a favorite plush chair, are prime sites for dust mites. The top part of mattresses containing fibrous material is a favorite place for dust mites during warm and humid times. The deeper parts of mattresses may provide protected areas for the dust mites during unfavorable conditions. Clothing is used by dust mites as transportation from room to room or even from house to house.
Control of dust mites can be difficult, time consuming, and expensive. For people who are extremely sensitive, the following measures should be taken:
Installing HEPA filters on air conditioner or heater vents is not practical or necessary, and may actually increase mite problems. Remember, dust mites cannot survive on the dust in the ducts, and the small holes of the filters will force air out of vents at a higher velocity, stirring up more dust than without filters.
Complete elimination of dust mites is unlikely. Reducing populations is the only likely way to reduce allergens in the air. Reducing humidity in the home by using a dehumidifier may help reduce populations, but reducing humidity levels in microclimates, like in bed fibers or carpet fibers, is impossible. Chemical control is not necessary, nor will it have a lasting effect on dust mite populations. Regular cleaning and vacuuming will have a greater impact.