It is designed to stop wrinkles, but Botox can also protect people from infection with Covid, according to a new French study.
The researchers said that of the nearly 200 patients who injected Botox by July last year, only two had Covid symptoms.
But experts described the study as "poor" and insisted it did not prove whether Botox made any promises to fight Covid.
More than one million Britons receive Botox injections each year, and the procedure is even more common in the US.
Toxin, one of the most dangerous elements known to science, helps reduce wrinkles because it relaxes muscles.
But it is also used for medical reasons, and is given to patients suffering from migraines and involuntary muscle contractions, to help relieve symptoms.
About 193 patients were included in the study, of whom three-quarters were women (146). They were on average in their fifties.
All volunteers were followed for three months after receiving the injections to see if they were infected with the virus.
None of the participants ever tested positive with Covid.
"Our results show a significant difference between the number of infected individuals in the general population and the number of Botox-injected patients who showed signs of Covid."
They acknowledged that the region from which patients were selected was not "one of the most affected areas" in France, "but quite the opposite".
Professor Eillem van Schaik, director of the Institute of Microbiology and Infection at the University of Birmingham, criticized the study.
He told MailOnline: 'This paper can not be used as evidence, even as weak evidence, that Botox can defend against Covid.
He said on Twitter: 'Extremely poor articles about Covid continue to be published in peer-reviewed magazines.'
