It is more celebrity than respiratory, but botox could prove a breath of fresh air for asthmatics if an Australian trial of the toxin launched Tuesday is successful.

Botox, or botulinum toxin type A, is usually used to smooth wrinkles by temporarily paralysing the muscles around the eyes and brow, but researchers at Melbourne's Monash University believe it could also be used to ease asthma.

Phil Bardin, director of respiratory medicine at the Monash Medical Centre, is preparing to test botox injections into the voiceboxes of severe asthmatics after the jabs were shown to be successful in curing vocal exhaustion.

A recent Monash study found half of severe asthmatics had voicebox problems similar to vocal cord dysphonia, suffered by those who have lost their voice through overuse and a condition which botox has been proven able to fix.

"We've discovered that in many of these patients they seem to have not only asthma of their lung but also of their voicebox," Bardin told AFP.

"The voicebox seems to close when it should be opening, and it almost spasms a bit like you find in the lung as well. This is an attempt to try and rectify that problem."

Under the world-first Australian trial, due to begin within weeks, 60 asthmatics will receive injections into one of the muscles of their voicebox -- 30 of whom will get botox and the rest a placebo.

It would not cure the underlying lung tightness associated with asthma but would hopefully ease the symptoms, Bardin said.

There have been one-off success stories with the treatment internationally, he said, but the Monash trial will be the first formal study.

Botox had been used about 400 times by another Monash physician on dysphonia patients, relaxing and reprogramming their vocal muscles to work properly and restoring their voice.

Temporary quietness of the voice was the only common side effect, said Bardin, adding that his team were "reasonably reassured that it's safe".

"That whole process whereby the voicebox operates we're hoping will get reprogrammed," he said.

"So the muscles will work again after three months but we're hoping they will work in a normal way rather than in a spasmodic, spastic type of fashion."