Writing in The Lancet journal, Gary Borodic, a poison expert, describes the case of an 80-year-old woman who received botulism injections to control muscle spasms.

She had been receiving the treatment for 13 years, but suddenly developed classic botulism poisoning symptoms.

She had severe difficulty swallowing. Her face became paralysed and she could not fully close her eyes.

She lost 23 pounds over three weeks and had to be fed through a drip.

The woman had to spend 10 weeks in hospital.

Gary Borodic said she suffered an allergic reaction to the botulinum toxin injections.

Excessive sweating

The case could have implications for other conditions treated by botulinum toxin, including wrinkles and sweaty palms.

Botulism can cause severe food poisoning. Between 1910 and 1919 70% of people who had botulism poisoning died. By 1990, this number had been reduced to 9% and by 1993 to 2%.

Symptoms of poisoning include double vision, poor reflexes, difficulty swallowing and problems breathing.

Botulinum toxin can help to control involuntary muscle spasms. It can also be injected into under-arm areas and palms to control excessive sweating.

And some plastic surgeons inject it in minute doses to temporarily weaken frown muscles.

They say it can get rid of unwanted lines for up to nine months.