Dental experts in Leeds say the powdered drugs inhaled by increasing numbers of children are sufficiently acidic to dissolve the enamel surfaces of teeth.

They say doctors should advise children to rinse their mouths with water directly after taking the drugs.

"Children should also be encouraged to clean their teeth thoroughly at least twice a day with a fluoride toothpaste," they write in the British Medical Journal.

"This would help to prevent dental erosion, which may cause considerable sensitivity and is both costly and time consuming to treat."

Significant erosion

A previous study has already shown that asthmatic children have significantly more erosion of their teeth than children without asthma.

Elizabeth O'Sullivan and colleagues from the Department of Paediatric Dentistry at Leeds Dental Institute tested the pH of the main asthmatic drugs on the market and found the powdered forms to be more acidic than the aerosol varieties.

Nearly all the powdered drugs had a pH of less than 5.5 - the level of acidity at which tooth enamel begins to dissolve.

"This is just an initial finding and we are going to look at the issue in more detail," said Ms O'Sullivan.

"We're planning to carry out more research to look specifically at children and the effects of the inhalers in their mouths because this was just looking at the inhalers themselves."

Early warning

She said the erosion could be caused by a number of different factors including diet, other medication and acid from the stomach. But the high incidence of erosion in asthmatics meant the inhaled drugs needed to be investigated.

This is an "early warning" of the potential problem, she said.

"Obviously, we're not encouraging children to stop using the drugs, but the main thing is that they rinse the mouth out after they use the drug."

Mouth gargle

The National Asthma Campaign said the study was "interesting" and required further investigation. It said people who use the drugs should be rinsing their mouths and brushing their teeth regularly anyway.

"With inhaled steroids, what we don't want is any medication which is left in the mouth being swallowed," said Anne Pearson from the campaign.

"So what we do advocate is that patients gargle and spit out. It's one of those messages about having to weigh up the benefits of asthma treatment compared to the possible associated risks.