House dust mites are microscopic bugs that primarily live on dead skin cells and 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 dust mites with bed bugs. 

Skin cells and scales, commonly called dander, are often concentrated in lounging areas, mattresses, frequently used furniture and associated carpeted areas, and often harbor large numbers of these microscopic mites. Since the average human sloughs off 1/3 ounce (10 grams) of dead skin per 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. Nearly 100,000 mites can live in one square yard of carpet.

A single dust mite produces about 20 waste droppings each day, each containing a protein to which many people are allergic. 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.

Beds are a prime habitat, as roughly one-third of life occurs there. About 80 percent of the material seen floating in a sunbeam is actually skin flakes. Also, bedroom carpeting and household upholstery support large mite populations.

Are mites harmful? What do they do?

For most people, while they are unappealing, house dust mites are not actually harmful. However, the medical significance of house dust mites arises because their microscopic cast skins and feces are a major component of house dust, which induces allergic reactions in some individuals.

There is a genetic predisposition to dust mite allergies, but like many allergies it can also develop over time. It is believed by allergists that between 18 to 30 percent of Americans are allergic to dust mites’ waste products, and nearly 50 percent of American homes have allergen levels that are high enough to cause sensitivity in people who were not previously allergic to dust mites. In other words, high levels of dust mites and their wastes, can cause previously non-allergic people to develop an allergy.

In addition to producing allergic reactions, dust mites can also cause nasal polyps to grow within the nose.

House dust mites are too small to be visible to the naked eye; they are only 250 to 300 microns in length and have translucent bodies. It takes at least a 10X magnification to be able to correctly identify them.

Through the microscope, one will see many oval-shaped mites scuttling around and over one another. They have eight hairy legs, no eyes, no antennae, and a tough, translucent shell, giving a fearsome appearance.

Detection

House dust mite presence is often suspected before they are actually seen and accurately identified. 

The presence of house dust mites can be confirmed microscopically, which requires collecting samples from mattresses, couches or carpets. Also, it requires the use of a microscope with sufficient magnification and the technical ability to recognize house dust mites under the microscope.

In general practice, testing is unnecessary. Dust mites are extremely common in household environments, and therefore nearly always show up in a test, so testing just adds expense. A better question than “are dust mites present?” is, “How can I control or remove them?”