The trend toward alternative therapies for children who have asthma is leaving those kids worse off, according to a study of their parents' practices.

For parents who reported using an alternative asthma therapy, their children were twice as likely to have poor control of the asthma than the children of parents who didn't use these therapies, Canadian researchers found from their eight-year study.

The most commonly reported alternative therapies were supplemental vitamins, homeopathy and acupuncture.

The researchers from the University of Montreal said that over the study period beginning in 1999, the number of parents who reported using an alternative therapy remained stable, at about 13 percent. The rate is about five times higher in the United States, they said.

"Previous studies have shown that close to 60 percent of parents believe that complementary and alternative medicines are helpful. Yet well-designed studies have failed to show any evidence that therapies such as acupuncture, homeopathy, chiropractic medicine or herbal therapy are effective in asthma," Francine Ducharme, a professor at the university, said in a statement.

Conventional therapies for children who have asthma include government-approved medications administered through inhalers and nebulizers.

Ducharme said parents may not be aware that the use of alternative medicines comes with risks , including adverse reactions and possible interactions with conventional therapies.

The study was based on questionnaires completed by more than 2,000 families who came to the Asthma Centre at the Montreal Children's Hospital. Parents were asked if they used any form of alternative medicine to help alleviate their children's asthma, and to specify the type of therapy they used.

It was "particularly troublesome," Ducharme said, that most of the children who received these therapies were younger than 6, because preschoolers suffer more asthma flare-ups requiring an emergency department visit than do all other age groups.

Ducharme said that parents considering alternative or complementary medicine should discuss it with their physicians, and that health care professionals should ask parents about their alternative therapy use, especially if a child's asthma is not well controlled, and should initiate appropriate counseling.

The findings, which were published in the July/August issue of the Canadian Respiratory Journal, were not widely reported. The researchers recently issued a news release about their work.