Dust mites: Common cause of allergy symptoms

If you're sensitive to house dust, you know that even a single whiff of dusty air can trigger allergy symptoms and asthma. But dust itself probably isn't the cause of your misery. Instead, dust mites — microscopic creatures that live in dust — are the most likely culprits.

Dust mites inhabit even the cleanest homes. The residue dust mites leave behind — droppings and decaying carcasses — mixes with dust and becomes airborne. If you aren't allergic to dust mite residue, it's not harmful. But if you are, it can make you sneeze and wheeze year-round. Dust mites are one of the most common causes of perennial asthma and allergy symptoms.

Although you can't completely eliminate dust mites from your home, you can reduce their numbers and decrease the amount of residue that gets into your air, which may help you breathe easier.

Dust mites: A common, invisible nuisance

Too small to see with the naked eye, dust mites resemble their distant relatives, spiders and ticks. Unlike spiders and ticks, however, they don't bite. And unlike some other species of mites, they aren't parasites that live on plants, animals or people.

The common dust mite, shown magnified approximately 2,000 times in this scanning electron micrograph image.

Dust mites live in houses for the same reasons you do: because houses provide all of their necessary creature comforts. They like warmth — ideally, a room temperature of 75 to 80 F. And they thrive in moist environments — preferably 70 percent to 80 percent humidity. Since they can't drink, they get the water they need by absorbing moisture from the air.

Even if you live in the mountains or desert — habitats usually unfriendly to dust mites — you may have dust mites in your home if you humidify your air. They're so adept at moving around, hitching rides on you, on your pets or in infested fabric, that they usually colonize new houses within a few years.

The typical home supplies dust mites with abundant food and shelter. They eat dead skin cells, and they nest in dust-collecting fabric and furnishings. Ideal habitats include mattresses, pillows, carpets, upholstered furniture, bed covers, clothes and stuffed toys.

Your bed is especially inviting to dust mites. To them, it's a warm, cozy, all-you-can-eat buffet that's restocked every night with yummy food. Without knowing it, you may be sharing your bed with anywhere from 100,000 to 10 million of these uninvited guests.

How dust mites cause allergies and asthma

As dust mites proliferate, so do concentrations of the residue from their feces and decaying bodies. If you're sensitive to this residue, you may develop signs and symptoms of hay fever, such as sneezing, runny nose and itchy, watery eyes.

If you have asthma, high concentrations of dust mite residue can trigger frequent and severe asthma signs and symptoms such as lung congestion, wheezing and shortness of breath. You may be especially prone to asthma attacks at night, when you're lounging on a mite-infested sofa or sleeping in a mite-infested bed.

If you suspect you're allergic to dust mites, see your doctor for an evaluation. Allergy skin tests — which expose your skin to purified extracts of allergy-causing substances — can help your doctor determine whether you have a dust mite allergy.

Ridding your home of dust mites

Environmental control is the most effective way to treat a dust mite allergy. While it's impossible to rid your home of all dust mites, you can reduce their population by cutting off their sources of food, water and shelter. If you also adopt rigorous cleaning practices, especially in your bedroom, you can reduce dust mite residue to a level where it no longer causes symptoms of allergies and asthma.

To control dust mites:

• Encase your mattress, box springs and pillows in allergy-proof covers. This deprives dust mites of a primary food source: your dead skin cells. It also prevents dust mite residue from escaping from your bedding when you toss and turn.
• Wash sheets, pillowcases and blankets at least once a week. To kill dust mites, wash bedding in water heated to at least 130 F. If you set your water heater at a lower temperature to protect young children from accidental scalding, take your bedding to a laundromat that uses a higher temperature.
• Remove carpeting and use hardwood or linoleum flooring. This eliminates an ideal dust mite habitat. If removal isn't an option, choose a low-pile instead of high-pile carpet. It may help to steam clean carpeting at least once a year. Treating carpets with tannic acid or benzyl benzoate can remove some dust mite residue, but such chemicals must be applied repeatedly and can worsen allergies in some people.
• Dust and vacuum your house at least once a week. Use a damp mop or rag on hard floors and furnishings because dry cloths stir up dust mite residue. Vacuum carpets, sofas, curtains and window blinds with a vacuum cleaner that has a high-efficiency particulate air (HEPA) filter.
• Reduce humidity with air conditioners and dehumidifiers. If you can lower the relative humidity in your house to 50 percent or below, dust mites can't absorb moisture from the air, so they shrivel and die.
• Banish furry and feathered animals from your bedroom. This deprives dust mites of another primary food source: your pets' dead skin cells. So it's best to either have your pets sleep outdoors or in another room as far as possible from your bedroom. Regularly clean pets' sleeping areas and encase their sleeping cushions in allergy-proof covers.
• Cut out the clutter. Anything that collects dust also collects dust mites. Remove knickknacks, tabletop ornaments, stuffed toys, books, magazines and newspapers from your bedroom and minimize dust collectors in other rooms.

Although air filters can effectively remove other allergy-producing substances such as pollen, mold and pet dander, they're not an effective tool for controlling dust mite residue. Unlike some other allergens, dust mite residue is relatively heavy, so it stays airborne for only about 15 minutes.

Medical treatments for dust mite allergy

If environmental control of dust mites doesn't relieve your symptoms of allergies or asthma, your doctor may recommend that you take certain allergy or asthma medications.

Nonprescription hay fever medications include short-acting antihistamines (Benadryl, Claritin, others), decongestants (Sudafed, Chlor-Trimeton, others) and a nasal spray containing cromolyn sodium (NasalCrom). Prescription hay fever medications include longer acting antihistamines (Zyrtec, Clarinex, others), nasal corticosteroid sprays (Flonase, Nasonex, others) and a leukotriene inhibitor montelukast (Singulair).

Prescription asthma medications include inhaled corticosteroids (Flovent, Pulmicort, others), long-acting beta-2 agonists (Serevent, Foradil, others) and short-acting beta-2 agonists (Proventil, Ventolin, others).

If your symptoms are especially difficult to control, your doctor may recommend allergy shots (immunotherapy) to desensitize you to dust mites.