Indoor Irritants Contribute to Asthma

Strong medical evidence reveals that proteins shed by dust mites, cats and cockroaches can cause or aggravate asthma is some individuals.

Strong evidence reveals that proteins shed by dust mites, cats and cockroaches can cause or aggravate asthma in susceptible individuals, according to a committee of the Institute of Medicine (IOM) in Washington, D.C.

Secondhand smoke clearly aggravates asthma in preschool-aged children, but in older children, the relationship is less clear, according to the committee.

The group, organized at the request of EPA, analyzed dozens of potential indoor irritants and classified them according to the amount of research linking the substances with asthma.

"The prevalence of asthma continues to rise dramatically in this country and the reason why is a mystery," said committee chair Richard Johnston Jr., a professor at the University of Colorado School of Medicine in Denver.

"People spend most of their time inside and it's vital that we understand how the indoor environment may contribute to the disease."

There is "sufficient evidence" that fungi, molds, allergens from dogs and cold viruses, can aggravate asthma, but it is not clear if these irritants actually cause the respiratory disease.

Other factors show a "limited or suggestive association," meaning that at least one large study found an association between the substance and asthma, but the evidence is not yet conclusive of a link.

That category includes allergens shed by domestic birds, certain types of pneumonia, and other respiratory viruses.

Other factors that fit in this category are formaldehyde fumes and fragrances found in personal care and household products.

As for pesticides, houseplant spores or material from domestic or wild rodents, the research is still inadequate to determine if they are a major cause or aggravator of asthma.

To help prevent or control asthma in susceptible individuals, the committee recommends the following.

Remove pets and pests from the home.

  • Thoroughly and regularly clean bedding, carpets and upholstered furniture.
  • Eliminate chemical pollutants, including "a complete cessation of smoking in the home."
  • Control indoor humidity -- keeping it as low as possible.
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