BOSTON (Reuters) – Giving steroids to children who are wheezing because of viral or other infections does not help, researchers reported last week.

And an experimental treatment designed to prevent wheezing may be effective, but it seems to pose too many risks to be recommended, according to studies published in the New England Journal of Medicine.

About one-third of preschool children develop wheezing, which can worry parents. At least 75 percent outgrow the problem by age six. In the past, doctors have treated it as they would asthma, which is why they often use corticosteroids.

"It is clear that on the basis of these two studies, current practice must change," Dr. Andrew Bush of the Imperial School of Medicine and Royal Brompton Hospital in London wrote in a commentary. Dr. Jonathan Grigg of Queen Mary University in London and colleagues found that children given five days of the steroid prednisolone stayed just as long in hospital as children given a placebo. They tested nearly 700 children aged 10 months to five years old. Nor was there any difference in their symptoms over the next seven days, Grigg's team reported.

"If your child is very sick, it doesn't mean you shouldn't give oral steroids. But in the general run of things, for most kids at home or presenting to their doctor with moderate wheezing that doesn't require many days in the hospital, steroids are not going to be of any benefit," Grigg said in a telephone interview.

"I would have loved for steroids to work," Grigg added.

However, he said, the result "does fit into the general perception that preschool wheeze is very different from attacks of allergic asthma in older children and adults."

Bush wrote: "It is disturbing to contemplate how many unnecessary courses of prednisolone have been given over the years, in good faith, because we all assumed that preschool children are little adults. There is certainly a lesson there for the use of other medications."

The second study compared GlaxoSmithKline's Flovent, available generically as fluticasone, with a placebo in 129 children aged one to six years. At the first sign of nasal congestion, sore throat or other symptoms that might indicate an upper respiratory tract infection, the children were treated twice daily for up to 10 days.