Dust Mites and Allergies

In greatly enlarged photographs, dust mites look like something from a horror movie. Invisible to the naked eye, mites inhabit more than 80 percent of all U.S. households, no matter how clean and neat.

They are actually on the clean­up committee: they eat our discarded skin cells, as well as ani­mal dander, pollen, fungi, bacteria and other microscopic organic material in the domestic environment. They thrive in mattresses, pillows, carpets and clothing. Thousands of mites can live in just one gram of dust.

Dust mites don’t carry disease and don’t bite, fortunately, but they can trigger asthma, hay fever and skin reactions in some people.

In fact, dust mites are prob­ably the most common indoor allergen, especially in warm, humid climates and for people with asthma. They are virtually non­existent in very dry climates.

There’s a surprising amount of debate about how to reduce dust mites and the symptoms they cause. In recent years, much of the conventional wisdom has been called into question—mostly because of insuffi­cient or conflicting evidence and because other types of allergens are also often involved.

If you have asthma, a skin con­dition or other reaction you think might be caused by dust mites, consult a board-certified allergist for a diagnosis.

Consider these strategies

• Buy a good vacuum cleaner with a high-­efficiency particulate air (HEPA) filter. Ordinary vacuuming will only send dust mites and their particles into the air. It’s not clear how much a HEPA filter actually helps with allergies, but it’s worth trying. Ideally, if you’re allergic, get some­one else to vacuum and dust. Vacuum bags should be changed often, since mites and debris can get out.

• If your allergies are severe, remove carpets and upholstered furnishings, espe­cially in your bedroom.

• Install wooden or plastic blinds instead of drapes and curtains. Some products claiming to kill dust mites in carpets can irritate the respiratory tract.

• Wash bed linens and blankets in hot water and use a hot dryer. Very hot water is best. Dry cleaning may be less effective at killing mites—research is inconsistent.

• Use impermeable covers to encase mattresses, pillows and blankets that can’t be washed, which can harbor lots of dust mites. Studies have been conflicting about how much this helps, however.

• Replacing pillows periodically makes sense, which means you’re better off not buying pricey ones. Dust mites can infest all kinds of pillows—those made of feath­ers, polyester, foam or other synthetics. There’s no consistent evidence that one type is preferable.

• Try using a dehumidifier in the bedroom in damp climates, since dust mites thrive under humid conditions. In warm months, use an air conditioner, which helps lower humidity.

• Be sure bathrooms and laundry rooms are well vented—this reduces humidity in the rest of the house.  Don’t bother with air purifiers or air­duct cleaning services—they will do little or nothing to reduce dust mites.

Bottom line: These steps are hardly a panacea. Even if they do reduce dust mites, those that remain may still cause allergic reactions, especially if you have asthma and have become sensitized to the allergens. But the steps may at least help reduce your symptoms.