Botox injections can prevent children with cerebral palsy from suffering a distressing side effect of the condition, scientists have found.
Botox is used cosmetically to banish wrinkles
Injecting the toxin into the salivary glands reduced drooling, a common problem with the neurological disorder.
Doctors have already used botox to help control problems with muscle tension which often occur with cerebral palsy.
The Toronto Hospital for Sick Children team presented their findings at a medical meeting in New Orleans, US.
Botox is more commonly used by cosmetic surgeons to smooth out wrinkles.
The botulinum toxin type A can be deadly, paralysing muscles needed for breathing, but only very small doses are given in medical or cosmetic treatments.
It works by blocking the signal that nerves are trying to pass to the muscles.
A side effect is a dry mouth. But in the case of neurological conditions, such as cerebral palsy, where excessive drooling is a problem, this is actually helpful.
Dr Peter Chait and colleagues told an annual meeting of the American Roentgen Ray Society how injections of botulinum toxin A into the salivary glands helped 70% of children with cerebral palsy and severe drooling.
His team gave the treatment to seven children multiple times and at different doses. They then asked the children's parents and carers to fill out questionnaires so they could assess whether the treatment had helped.
Dr Chait said: "Now that we know it is effective, we are trying to optimise the procedure."
Dr Tony Ward from the North Staffordshire Rehabilitation Centre in the UK has been using botox injections for the same indication in adults with cerebral palsy and multiple sclerosis on an ad hoc basis.
He said the treatment was very effective and that the benefits lasted up to about 12 months before individuals needed repeat injections.
Typically, this involves one jab in front of each ear and another at the angle of the jaw on each side of the face.
"It is no more painful than a vaccine. But for children, it might be advisable to sedate them," he said.
He added: "It really does change people's lives. I had one patient who went through 120 boxes of tissues every month. Drooling can be very distressing."
Botox injections have also been used to treat excess sweating, called hyperhydrosis.
Richard Parnell, head of research at the charity Scope, said: "It is good to see that this treatment appears to help.
"Drooling can be quite a problem for these children."
However, he cautioned that severe drooling should only be treated if it was a problem for the child rather than for purely aesthetic reasons.
He also said it was important to involve the child in the consent process for the procedure.