Recently, researchers in coastal Australia -- which has a humid climate where house dust mite levels are high -- found that using special coverings on mattresses and pillows and specially washing other bedding reduced dust mite levels 30% after four weeks, and their levels remained about the same for the rest of the six-month trial.
It's not dust that causes people to wheeze and sneeze; it's the eight-legged arthropods, smaller than the period at the end of this sentence, that are natural inhabitants of indoor environments. The droppings of these mites are the most common trigger of continual, nonseasonal allergies and asthma symptoms, especially in humid regions, where dust mites tend to thrive throughout the home.
The most important finding, according to lead researcher Carl Vanlaar, PhD, is that even in an environment where house dust mites thrive, it is possible for people to substantially reduce the mites and the substances they produce that cause allergies, called allergens.
Using simple procedures, such as putting special coverings on mattresses and pillows and rigorously washing the rest of the bedding, can help you score points in the war against these Star Wars alien-like creatures, says Vanlaar, who is an allergen research scientist at the Institute of Respiratory Medicine at Royal Prince Alfred Hospital in Sydney. The study appeared in a recent issue of the Journal of Allergy and Clinical Immunology, with funding from the Asthma Foundation of New South Wales.
In the trial, researchers tested 14 beds in seven households. In half the beds -- occupied by children with allergy symptoms -- they washed all bed coverings with Acaril, a mite killer containing 30% benzyl benzoate as the active ingredient. They also vacuumed the bedding and floors, and covered mattresses and pillows with special coverings. The benzyl benzoate wash was repeated every two months during the trial and again four months later.
In the other seven beds -- which were occupied by the allergic children's siblings -- the researchers did nothing special. They found that there was a substantial reduction in the amount of allergen caused by dust mites in the study children's beds compared to the other children's beds.
There have been several other studies looking at ways of controlling mites and their allergens in the home. Some methods, such as the use of benzyl benzoate powders, have been very limited in their effectiveness.
"Studies targeting allergens in beds -- such as our own study -- have had variable levels of success depending on the [method] used, or the studies took place in climates unfavorable for dust mite survival, such as in northern Europe," says Vanlaar. He adds that in this test, they opted for washing the upper bed coverings rather than encasing them because when the upper covering is encased, the bed can become somewhat hot and uncomfortable.
Michael Ruff, MD, spokesman for the American Academy of Allergy, Asthma, and Immunology, agrees with the Australian findings. "This study proves that even allergy and asthma sufferers living in areas with high humidity can benefit from these steps." Ruff says washing bedding in extremely hot water once a week and encasing pillows and mattresses in allergen-resistant covers are the easiest and most effective ways to reduce allergen levels in the home.
Vanlaar says the next step is to test whether this method of allergen control in bedding is enough to reduce allergy symptoms in individuals with current symptoms of asthma, and to help prevent allergies and subsequent asthma in high-risk infants.
"We are already investigating the second item by conducting a large ... trial -- the Childhood Asthma Prevention Study -- in which we are treating the cots of approximately 300 babies who are in a high-risk group for asthma, based on a family history of asthma," by washing and encasing the bedding like they did in the current study.
To start your own grassroots campaign against the little critters, the American Academy of Family Physicians recommends that you follow these 10 steps for defeating dust mites in the home:
Start in the bedroom:
- Since most dust mites live in mattresses, put an airtight plastic or polyurethane cover on every mattress.
- Wash sheets and blankets in very hot water every week.
- Wash bed pillows every week or put a plastic cover on them. (The pillowcase goes over the plastic cover.)
- If possible, bedrooms should have a hardwood, tile, or linoleum floor. These surfaces are easier to keep clean than carpet.
- If you have to have carpet, try not to place the carpet on concrete. The warm space between a rug and concrete is a good place for mites to live.
- For carpeting, spray the rug with a solution of 3% tannic acid every two months to kill the dust mites. Ask your doctor how to use this solution, and whether it is right for your family.
In the rest of the house:
- Vacuum all carpets and upholstery every week. Vacuums with high-efficiency filters pick up more dust mites, but even standard vacuums work well.
- Furniture that has a polyurethane cover over its padding helps. Plastic or wooden furniture that doesn't have much padding can also help keep down the number of dust mites in the home.
- Because dust mites love warm, humid places, running your air conditioner and keeping the humidity low make a difference.
- Don't bother with special air filters -- they won't help children with asthma or allergies.