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Saying Good Night to the Dust Mite


You can’t see them, but they’re all over your home. Dust mites will be in the carpet, the sofa, the bedding, the curtains, even a child’s stuffed animals. These tiny insects, visible only under a microscope, leave a trail of waste that is a highly allergenic.

It’s estimated that between 10 and 25 per cent of North Americans are sensitized to dust mite droppings, and that these pests will spark wheezing in over 50 per cent of asthmatics. Thankfully, while you can’t get rid of dust mites completely, you can minimize their multiplying numbers.

What They Are

Dust mites, cousins to the spider, are tiny, eight-legged arachnids measuring only one-quarter to one-third of a millimetre in size. They spend their two to four months of life eating, creating waste and reproducing. A female will lay 100 eggs in her lifetime, and each mite produces about 10 to 20 waste pellets a day.

They are whitish in color, and thrive in warmth (between 75 and 80 degrees F; 24 and 26 degrees C) and humidity higher than 50 per cent. Mites eat minuscule flakes of human skin and animal dander. They can’t drink, but absorb moisture from the atmosphere.

Where They Live

Dust mites prefer a plentiful supply of skin flakes or animal dander, moisture and warmth. This is why you’ll find the highest concentration of mites in your bed. An average mattress contains between 100,000 and 10 million bugs.

A study in 2000 found that more than 45 per cent of American homes had detectable dust mite levels associated with the development of allergies, and 23 per cent had bedding with concentrations of allergen high enough to trigger asthma attacks.

What You Can Do

“The confusion about allergen avoidance is not about whether it really works, but whether it’s possible to do in an ordinary house,” says Dr. Thomas Platts-Mills, a professor of medicine and microbiology, and the chief of the division of allergy, asthma and clinical immunology at the University of Virginia Health System. “And the answer is yes, but it’s got to be done seriously.”

According to Platts-Mills, a leading dust mite researcher, there are a few keys:

• The most important plan of attack is to make sure your home is too dry for the mites to survive. Maintain a humidity level of between 40 and 50 per cent, and don’t use a humidifier, even in the winter. Consider purchasing a hygrometer (available at most major building supply stores for as little as $20) to monitor the level of moisture.

Platts-Mills adds that basements are tough to keep dry, “so don’t live in basements if you’re mite allergic.”

• A recent European study discovered that older mattresses and poor ventilation, along with sleeping on lower floors of a home, contribute to higher concentrations of dust mites in mattresses. Platts-Mills considers a mattress used for more than five years to be old, depending on how it has been treated. Ensuring that your bedroom has proper ventilation, is not in the basement or too humid, and replacing your mattress (unless it has been covered with dust-mite impermeable covers the whole time) every few years will diminish the number of mites that bunk in with you.

• Encase your mattress, duvet and pillows in mite-proof covers. Plastic is best for containing mites, but not the most comfortable to lie on. A cozier option is tightly woven fabric covers, which are usually made from polyester or a cotton/poly blend and are designed to hold up to frequent washings. Several brands are now on the market, and some have passed rigorous allergy/asthma certification.

• Though asthmatics and those with dust mite allergies have long been told to use synthetic-filled pillows and duvets, research has emerged over the past few years that indicates feather bedding may be a better option. This is because the tightly woven cotton used to keep the feathers from poking through the fabric casing also acts as a barrier to mites.

• If using plastic bed covers, wipe them down once a week with a damp cloth, and let them dry completely before dressing the bed. Cloth bedding, including fabric mite-blocking covers, should be washed weekly in water at least 130 degrees F.

Next Page: Cleaning, Flooring and Pesky Toys

• Snuggly stuffed animals can harbor just as many mites as a pillow. Every eight weeks or so, place the toys in the freezer for 24 hours. Follow up with a spin in the washer and dryer (cool temperatures are OK because the freezing kills the mites). Also look for toys labeled with the Asthma Friendly brand, a line that’s received the sanction of the Asthma and Allergy Foundation of America (AAFA).

• Mites have sticky feet that cling to soft surfaces like carpet fiber and upholstery. While a good quality HEPA filter vacuum will reduce their numbers, Platts-Mills says vacuuming alone can’t resolve the problem of dust mites in the carpet. Avoid wall-to-wall carpets and opt for hardwood, tile or vinyl flooring if possible, and minimize plush furnishings.

• Clean all hard surfaces at least once a week with a damp cloth, and get rid of clutter that will attract mites. Use a HEPA filter-equipped vacuum to rid the house of dirt and pollen, and to deprive the mites of their food source: skin cells shed by the family and the pets.

• As for HEPA air-filtering devices, while they’re great for dealing with smoke and lightweight pollen and dander, Platts-Mills says that because dust mite allergen doesn’t remain airborne for long, they aren’t effective for this allergy.

Platts-Mills has seen first-hand how effective these techniques can be for those with dust mite allergy and asthma. “Over my career, hundreds of my patients have changed their lives,” he says. “They get it right, and I never see them again.”

General statistics/studies: Prevalences of positive skin test responses to 10 common allergens in the U.S. population: Third National Health and Nutrition Examination Survey [2]; First National Allergen Survey [3]; Distribution and Determinants of House Dust Mite Allergen in Europe [4]: The European Community Respiratory Health Survey II.


First published in Allergic Living magazine.
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