Study shows reducing dust, other allergens could cut kids' asthma.

Controlling exposure to common household allergens and irritants, such as dust mites, cats, and tobacco smoke, would significantly reduce the number of asthma cases in children, according to researchers at the University of North Carolina at Chapel Hill School of Medicine.

A study of 343 elementary school-aged children published in the June issue of the American Journal of Respiratory and Critical Care Medicine showed a few indoor allergens strongly promoted wheezing and asthma.

"It has long been known that asthmatic children are frequently allergic children," said Dr. Fred Henderson, professor of pediatrics and co-investigator of the study. "We wanted to know exactly which allergens were closely linked to asthma and estimate possible benefits of environmental interventions to prevent asthma."

In the study, 90% of children with recurrent wheezing, often identified as asthma, had positive skin tests for allergies.

Asthma affects more boys than girls and includes recurrent episodes of difficult breathing, chest tightness, and wheezing. Almost 10% of youngsters have asthma, the leading cause of chronic illness in children.

Asthma has more than doubled in the last two decades, studies show. The Centers for Disease Control and Prevention has reported that deaths from the condition, which kills nearly 1,500 children in the United States each year, rose nearly 50% in the 1980s.

"Our study suggests that controlling specific indoor exposures and tobacco smoke could reduce the prevalence of asthma by more than 50%," said Henderson, staff pediatrician at the UNC-CH's Frank Porter Graham Child Development Center.

Dust mites, unseen but common inhabitants of upholstery, carpets, mattresses, and bed linens, were by far the most prevalent allergen in asthmatic children in the study. Eighty percent of subjects with asthma symptoms were allergic to the tiny arachnids.

Dust mite allergy increased the risk of wheezing approximately eight-fold, according to the study. Children whose asthma is triggered by house dust mites are allergic to a protein found in mites' gastrointestinal tracts and droppings.

"Asthmatic children who are allergic to dust mite allergens should sleep in beds with plastic covers on the mattress, box springs, and pillows," Henderson said. "In addition, all bedding, including blankets and mattress pads, should be washed in hot water at least every two weeks. Stuffed toys should be either washable in hot water or removed from the bed. When possible, carpets should be removed from the bedroom. "

Cat allergies, although less common, increased the risk of asthma symptoms approximately 15-fold.

"Pet allergies should not be viewed as trivial for the child with asthma," Henderson said. "If the family of a child with asthma does not own a cat or dog, these exposures should be avoided. Decisions regarding continued pet ownership by such families should be made carefully."

Allergic children exposed to tobacco smoke were three times more likely to have asthma than non-exposed children, according to the study.

"Exposure to tobacco smoke in the home is the most common modifiable factor that increases the risk of asthma symptoms in allergic children," Henderson said.

Ironically, although pollen sensitivity was the second most common allergy, it did not increase the likelihood of having asthma symptoms. The study also showed that breast-fed babies were not less likely to be allergic or have asthma later in life.

A history of respiratory illness during infancy was only a slight predictor of asthma later, according to the UNC-CH study. A family history of asthma was a significant predictor.