It is one of UK's most popular cosmetic treatments: the "no-scalpel facial", smoothing out the foreheads of everyone from yummy mummies to stressed-out politicians. But new research suggests that the deadly poison in Botox jabs may actually be able to spread from the face to the brain.
Researchers from the Italian National Research Council's Institute of Neuroscience who injected botulinum toxin into the faces of rats found that it moved away from the site of the injection and could be detected just days later in brain stem cells. The poison was not only still present in the rats' brains six months later, but was able to travel from one region of the brain to another.
"We suspect that this spread is a common occurrence after toxin delivery," said Matteo Caleo, who led the study. He pointed out that even minute quantities of botulinum toxin – which is one of the most poisonous substances in the world – are enough to interfere with nerve signalling elsewhere in the body.
Celebrities including Sir Cliff Richard, X Factor judges Simon Cowell and Sharon Osbourne, and Desperate Housewives star Teri Hatcher have admitted to using Botox injections, which work by temporarily paralysing facial muscles, reducing the contractions that cause new wrinkles and ironing out existing ones. While the procedure was once the preserve of celebrities and the wealthy, Botox shots are now available from cosmetic surgeons and beauticians for as little as £99.
The latest findings come two months after the drug was linked to 16 deaths in the US, thought to have been caused when Botox used to treat muscle spasms migrated from the injection site to other parts of the body, weakening the muscles used for breathing or swallowing. This new research will be seized on by campaigners demanding tighter regulations on Botox, first approved for commercial use in 1989.
As it is a comparatively new treatment, knowledge of the long-term side effects is limited, although droopy eyelids and expressionless "frozen faces" are common. Despite these uncertainties, many practitioners have questioned the significance of the latest findings.
"There is no chance that this could happen to a human," said Dr Douglas McGeorge, president of the British Association of Aesthetic Plastic Surgeons. "Botox is a poison and a single unit of botulism is a 50 per cent lethal dose for a white mouse, but it is very different for human beings. The doses [used here] are relatively much smaller and it has much more local effects.
"If used appropriately, Botox is a wonderful drug, and you are much more likely to encounter problems from injecting it into the wrong area than from it migrating anywhere."