If you have been diligently vacuuming your carpeting to rid your home or office of allergy-causing dust mites, a new study suggests all that effort may be for naught.

Researchers in Australia have found that vacuuming carpet&mdashespecially old, worn carpets&mdashmay simply redistribute dust mite allergens rather than remove them. And people who hope to reduce their risk of asthma or allergic reactions through avoidance of allergens may not be accomplishing their goals.

"Allergen avoidance measures that rely solely on vacuum cleaning are likely to be of limited success unless more rigorous cleaning than standard home vacuuming is performed," lead researcher Jason Sercombe said in a press release.

Sercombe and his colleagues at the Woolcock Institute of Medical Research in New South Wales, Australia, measured the amounts of Der p 1 (the allergy-causing protein produced by dust mites) contained in samples of several used carpets. Protein levels were measured before and after they vacuum cleaned the carpets with two different kinds of dry vacuum cleaners. The researchers logged the vertical distribution of the proteins on the carpets.

They found that using vacuum cleaners with rotating brushes in the head helped to remove more dirt and dust mite allergens than cleaners without this type of equipment. Researchers noted that those brushes may also allow dust to be blown into the air if the suction component of the vacuum is not working properly. The carpets had been used for several years in homes that contained large amounts of the dust mite proteins throughout the depth of the carpet.

Several factors may contribute to the effectiveness of the vacuum cleaner, researchers said.

"Overseas studies have found that vacuum cleaners with two or three layer bags performed better than those with a single layer bag, and the maintenance of the cleaner and integrity of seals and gaskets were important factors in effective cleaning," Sercombe said. "There are many vacuum cleaners on the market that claim to be suited to allergy sufferers. The most important aspect to look for is HEPA (high efficiency particulate air) filter filtration, which is finding its way into some very affordable models."

Dust mite allergens can be reduced in the home by:

• When dusting, use damp mops and cloths to pick up all excess dust. Dry cloths should not be used to dust because they stir up allergens.


• Wash bedding (including pillows) at least once a week in water that is at least 130 degrees Fahrenheit (54 degrees Celsius). This will kill most dust mites that are present. Bedding that is not washable can be dry cleaned or left overnight in the freezer to kill dust mites. Also, use synthetic bedding materials. Dust mites prefer wool, feathers and cotton. Use allergen-impermeable covers on mattresses, pillows and box springs. These completely encase the mattresses and pillows and prevent mites and their waste particles from getting into the air. Tape over zippers.


• Keep pets out of the bedroom at all times. Dogs and cats attract dust mites like magnets.


• Use washable materials such as roll-type shades for window coverings. Those who use curtains should choose lightweight materials, which hold less dust. Vacuum window treatments often and wash them every six weeks.


• Dry laundered sheets, blankets and rugs in the sun. Sunlight destroys dust mites. However, this is not a good idea for people who also have allergies to outdoor allergens such as pollen.


• Frequently wash pets' sleeping cushions and encase the cushions in allergen-proof covers. Do not keep large stores of books and newspapers, which collect dust. Use plastic bags to cover clothes in closets, reducing dust accumulation.


• Try to limit the use of carpets and rugs, especially in the bedroom. Hardwood floors, tile and linoleum are easier to clean and keep dust-free. Low-pile carpets are preferable to deep-pile carpets. Frequently steam-clean carpets. Better yet, use throw rugs, which can be easily washed in hot water.


• Consider leather upholstery, which is less attractive to dust mites than upholstered furniture.


• Keep toys out of a child's bedroom, as they are likely to accumulate dust. Avoid stuffed toys and store all toys in closed containers, such as a toy box.