Q. My daughter is allergic to dust mites. We wash her sheets in hot water and she takes allergy medication but nothing really seems to help. Is there something you could use (or we could buy) to treat her bed to kill the mites?

A. Unfortunately, most of the studies looking for ways to reduce allergic reactions to house dust mites have shown very little positive effect from spraying with chemicals. To my knowledge, there is only one pesticide registered for use on dust mites and it cannot be used on beds. The dust mite allergens that cause the allergic reaction are from the presence of live and dead dust mites, their shed skins, and their feces. The best controls for dust mites are frequent cleaning of surfaces and bed linens, and the possible use of special bed encasements – although neither of these is a sure cure. The cleaning is not just to remove dust mites themselves but also to remove the house dust that the mites feed on which is made up of shed skin flakes from people and pets, bacteria, and mold.

Beds and Linens –Encasements are zippered covers that completely enclose mattresses, box springs, even pillows to prevent dust mite allergens (or bed bugs) from reaching the individual. You can order dust mite encasements on line and can even find them in certain stores like Bed, Bath and Beyond. Make sure you choose quality; it’ll probably cost you a couple of hundred dollars to get the complete set. Make sure you get washable encasements. One research study pointed out the importance of frequently (monthly) washing the encasements or they can accumulate dust mite allergens, too. If you don’t use encasements, turn mattresses frequently and air them out for a while after you strip the sheets. Replace down pillows with washable synthetic pillows. Wash blankets, sheets, bedspreads, drapes, and pillows frequently.

Floors –Get rid of any rugs in the bedroom. Dust mites and mite allergens can build up and get stirred up by walking and vacuuming. Most studies show unacceptable allergen levels as long as there is a rug in the room. If you keep the rug it needs to be vacuumed weekly with a vacuum equipped with a special HE (high efficiency) filter. Even without a rug, the floor has to be cleaned regularly and kept free of dust. To clean a bare floor without stirring up dust, damp mop it or use an electrostatic mop rather than a vacuum cleaner.

The Rest of the Bedroom –Whenever possible, eliminate fabric items, including curtains and stuffed animals, from the bedroom unless they can be washed frequently. Air out throw pillows in the sun every once in a while. Dust surfaces with a damp or electrostatic cloth 2 to 3 times weekly. Upholstered chairs are another thing to avoid in the bedroom since they are difficult to clean.

Room Air –Some studies have shown that special allergy air cleaners actually do reduce mite allergens. But avoid electronic or ultrasonic devices that claim to get rid of dust mites. They do not work against dust mites.  Dust mites thrive in humid conditions and warm temperatures, so dehumidifiers can sometimes help. Strive to get the relative humidity in the room below 45%. Cooler room temperatures (below 70°F) slow down dust mite reproduction, too. Keep room air circulating.