Defensive barriers

One of the most common sources of year-round allergies are tiny creatures called dust mites that are found in almost every home. These little critters feed on the skin we shed. It's not dust mites themselves that cause problems but their droppings, which contain proteins that can trigger allergic symptoms in susceptible people.

Mattress and pillow covers are designed to provide a barrier between people and dust mites, but two studies published in the New England Journal of Medicine last year found that while the coverings reduced exposure to dust mite allergens, they had little impact on allergic symptoms.

This does not mean that bed and pillow covers are a waste of money, though, according to an author of one of the studies.

"We think that the use of encasings still has a place in a set of measures to diminish contact with house dust mites," says Dr. Roy Gerth van Wijk, of Erasmus Medical Center in the Netherlands.

A spokesperson for the American Academy of Allergy, Asthma and Immunology (AAAAI) agrees that bed covers are just one part of a comprehensive anti-allergy program.

People with allergies must recognize that "allergen control is not going to fix the problem," says Dr. Pramod S. Kelkar of Allergy and Asthma Care of Indiana in Indianapolis. He recommends that anyone with allergies see a physician for a complete evaluation. While allergy medications may be necessary to control symptoms, there are several steps people can take to minimize exposure to allergens in the home, according to Kelkar:

• If it is a hard surface, wipe it clean of dust on a regular basis.

• If it is a washable fabric, wash it in hot water to kill dust mites. Sheets and bedding should be washed once a week.

• If it cannot be washed, then encase it. For pillows and mattresses, covers should be woven tightly to keep dust mites out but not so tightly that you cannot breathe through the fabric. Plastic covers keep dust mites out, but they are not as comfortable as fabric covers.

• If you can't wipe, wash or encase it, then remove it. If at all possible, carpets should be removed from bedrooms.

Clearing the air

Chemical products, such as acaricides and tannic acid, which kill dust mites or neutralize their allergens, may provide some benefits, but they are not as effective as washing or covering bedding, according to Kelkar.

Acaricides have little or no role in fighting allergens, according to Dr. Robert A. Wood, the director of pediatric allergy clinics at Johns Hopkins University School of Medicine in Baltimore. What's more, he says, these products "are not very easy to use."

Air cleaners that filter irksome allergens from the air are appealing to many allergy sufferers, but they may offer little benefit, experts say.

In one study, Wood and his colleagues at Johns Hopkins did find that a popular type of filter called a HEPA air cleaner reduced levels of cat allergens in the air by about 70 percent. That may sound impressive, but "that change did not result in any change in symptoms," says Wood.

He notes that there are three major types of air cleaners: HEPA cleaners, electrostatic cleaners and ionic cleaners.

Research on the cleaners is sparse, but HEPA devices are probably the best, says Wood, with electrostatic air cleaners possibly as effective for some allergens. Ionic air cleaners, which have risen in popularity recently, seem to be much less beneficial, according to Wood.

Taking simple steps

But for the most part, "filter systems don't work that well," says Dr. Richard F. Lockey, a professor of medicine at the University of South Florida College of Medicine in Tampa. He likens allergens in the home to an oil spill.

"You want to stop the problem, not have the problem and clean up afterward," says Lockey, who is also an AAAAI spokesperson.

Instead of filters and chemical allergen killers, Lockey advises people first to take more basic steps, such as covering mattresses, box springs and pillows.

"We want very complicated solutions," says Lockey, but "these things are very simple." The Florida physician says that one of the best ways to minimize allergens involves little more than elbow grease: spring cleaning.

"That is probably the best thing people could do to reduce the dust mite debris and other allergenic debris," says Lockey.

Of course, it may be a good idea for people with allergies to run by the hardware store to pick up a face mask before cleaning up the house.