Increasing preventer medication at the time of an asthma flare-up should not be recommended for children, a study suggests.

Significantly increasing a child's use of inhaled steroids at the first signs of an asthma flare-up is ineffective and may be associated with slowing their growth, an international study has found.

Published in the New England Journal of Medicine, the US research challenges the practice of increasing the dosage of inhaled glucocorticoids (preventer medication) by five times when asthma symptoms begin to worsen among children with mild-to-moderate asthma in a bid to avoid exacerbation.

Paediatric respiratory specialist Dr Louisa Owens, a spokesperson for the National Asthma Council, said the practice is not part of current childhood asthma treatment recommendations here in Australia.

However she said the research is concerning and warrants caution because of the potential for "significant harm" especially for teenagers with asthma.

According to Dr Owens, the adult asthma guidelines, which do recommend increasing inhaled steroid use during a flare-up, are often used for adolescents.

"Inhaled corticosteroids are generally considered quite safe so I think it is very concerning with very short periods you are still seeing significant height deficits in children in this study," said Dr Owens.

The researchers at the University of Wisconsin School of Medicine and Public Health studied 254 children aged 5 -11 with mild-to-moderate asthma for nearly a year.

For the randomised, doubled-blinded trial all children were treated with low-dose inhaled glucocorticoids (two puffs from an inhaler twice daily). At the earliest sign of a asthma flare-up the researchers continued giving low-dose inhaled steroids to half of the children and increased to high-dose (five times the standard) in the other half, twice daily for seven days during each episode.

The rate of asthma exacerbations among the two groups were not significantly different despite the intervention group being exposed to 14 per cent more

Though the children in the high-dose group had a 14 per cent more exposure to inhaled steroids the number of asthma symptoms, the rate of exacerbations and use of reliever medication albuterol, such as Ventolin, were all similar between the two groups, according to the study.

However the growth rate of children in the high dose group was about about 0.23 centimetres per year less than the rate of growth for children in the low-dose group.

"In children with mild-to-moderate persistent asthma treated with daily inhaled glucocorticoids, quintupling the dose at the early signs of loss of asthma control did not reduce the rate of severe asthma exacerbations or improve other asthma outcomes and may be associated with diminished linear growth," the authors concluded.

Lead researcher Daniel Jackson, associate professor of paediatrics at the University of Wisconsin said hoped the trial findings will better inform caregivers to make informed decisions about how to treat their young patients with asthma.