More than 14 million people in the United States have asthma , a disease characterized by inflammation of the airways, which makes breathing difficult. Although there is no cure for asthma, it can be controlled. Asthma medications can alleviate symptoms, including coughing, wheezing, chest tightness, and shortness of breath.

An asthma episode is usually triggered by something in the environment. For people who are allergic to dust mites, exposure to dust can trigger an episode. Exposure to dust mites may also trigger allergy symptoms in people with allergic rhinitis . Recently, hypoallergenic bedding that is impermeable to dust mite allergens has become widely available and physicians commonly recommend it to their patients. But, does it work?

Previous studies that looked at the effectiveness of this hypoallergenic bedding showed mixed results. A new study in the July 17, 2003 issue of the New England Journal of Medicine found that asthmatic adults who used hypoallergenic bedding experienced no greater improvements in airflow, asthma symptoms, or inhaler use than adults who used regular bedding. Using hypoallergenic bedding, however, resulted in a lower exposure to dust mites.

About the Study

The 1,112 study participants were between the ages of 19 and 50, had been diagnosed with asthma by a physician, and were regularly using corticosteroid inhalers, a common treatment for patients with moderate asthma.

Before the study began, researchers took blood samples to test for dust mite allergies and asked the participants about medication use, pet ownership, and smoking history.

For the first four weeks of the study, the participants logged their peak expiratory flow rate (PEFR, a measure of airflow), rated their asthma symptoms, and recorded their inhaler use. Then, the participants randomly received either hypoallergenic or regular mattress, pillow, and quilt covers, which were left on the bed for one year. No washing instructions or other information on the avoidance of dust mites was given to participants.

For the first six months after they received the bedding, the participants continued their normal inhaler use. During the second six months, participants were invited to participate in a program to reduce their inhaler use, during which they visited a nurse monthly.

Researchers visited a random sample of 10% of the participants’ homes after six and 12 months to collect dust samples from the mattress, which were tested for dust mites.

The Findings

Before the study began, 65% of the participants were allergic to dust mites, 55% had pets, and 24% were smokers.

After six months, even though the PEFR improved significantly in both groups, there was no significant difference between the two groups. There was also no difference in symptoms or use of inhalers.

After one year, 14% of the participants had completely stopped using an inhaler, and almost 50% were successful in the program to reduce inhaler use. However, there was no difference between the two groups in the number of participants who stopped or reduced their inhaler use. When the researchers only looked at the participants who were allergic to mites, there were still no differences between the groups.

The level of dust mites in the beds covered with hypoallergenic bedding was significantly lower than in beds covered with regular bedding after six months, but not after one year.

Another study in the same issue of the Journal showed that hypoallergenic bedding did not significantly improve symptoms in people who have allergic rhinitis, either.

How Does This Affect You?

These studies indicate that buying hypoallergenic bedding to manage asthma or allergic rhinitis is probably not worth the price.

In a previous study, taking multiple measures to reduce dust mites in the home—using hypoallergenic bedding, washing bedding in hot water every week, using powerful vacuum cleaners, and replacing carpeting with hard wood floors—helped reduce the incidence of asthma exacerbation. However, the authors of this study point out that doing all of these things is not practical for most people.

It is not clear why allergic subjects in this study showed no improvement with hypoallergenic bedding even though they were exposed to lower levels of dust mites. One possibility is that once an allergic individual has been extensively exposed to dust mites, a reduction in future exposures becomes less meaningful.

To find out if your asthma is triggered by indoor air quality, the American Lung Association suggests that you keep a diary to record when and in what situations you have episodes. After you identify suspected triggers of your asthma, focus on avoiding one at a time and see if you get better. By staying away from these triggers, you can help avoid asthma and allergy attacks. Possible triggers include:

  • Cold air
  • Tobacco and wood smoke
  • Perfume, paint, hairspray, and other chemicals that emit fumes
  • Allergen particles, such as dust mites, pollens, molds, air pollution, and animal dander