London: Botox, the popular anti-wrinkle jab, is unlikely to offer much benefit in the treatment of chronic migraine, say experts.
The injection has been licensed in the UK and US as a preventative treatment for chronic cases.
However, a review of evidence by the Drug and Therapeutics Bulletin said it could not "see a place" for giving Botox to migraine sufferers.
Migraine Action said patients should still be given the option of having Botox as some had seen improvements.
It is not clear how the neurotoxin works in chronic migraines but it is thought that it may block pain signals.
A trial of more than 1,300 patients showed success in reducing the frequency of headaches.
However, experts from the Drug and Therapeutics Bulletin, which reviews medical treatments in the UK, questioned the selection of patients in the trial, saying the diagnosis of chronic migraine was incorrect in some.
Botox leads to a worsening of headache symptoms in around one in 10 people, they said, with a similar number developing itching, rash, pain, stiffness and muscle spasms.
"These discrepancies and the limited evidence of benefit make it difficult for us to see a place for botulinum toxin A as treatment for chronic migraine," the BBC quoted authors as saying.