Five people are receiving emergency medical care in France for suspected botulism linked to eating pesto.

According to authorities in the Indre-et-Loire department in west-central France, a locally made brand of wild garlic sauce may have been contaminated with a dangerous toxin that can attack the nerves.

Cases like this are rare but potentially fatal, and can happen if homemade foods have been improperly preserved.

The French government issued an immediate recall of the product and has sent samples to a lab for analysis.

Authorities were trying to locate some 600 containers with the same “O P’tits Oignons” sauce before they are eaten, say officials.

The sauce is usually sold during local festivities or fairs.

The five patients are on respirators but conscious, spokesperson Patrice Latron told reporters.

“People who bought the same sauce must throw it out, destroy it,” Latron said.

Botulism is a rare but life-threatening condition caused by toxins made by clostridium botulinum bacteria.

These bacteria and its spores can live in soil, and are sometimes found on the surface of fruits, vegetables and herbs.

While the spores are generally harmless, they can grow into the bacteria that make the risky neurotoxins.

The neurotoxin is among the most toxic substances known – even tiny amounts can cause illness or death.

They attack the nervous system, and can cause paralysis. This can spread to the muscles that control breathing and can be fatal in five to 10% of cases if not treated properly.

There is an antitoxin that doctors can give.

Botulism illnesses have been linked to foods such as homemade pickles and garlic in oil.

Supermarket products undergo rigorous manufacturing processes to avoid contamination in preserved foods.

That bacteria is also used to make Botox – shots used by the cosmetic industry to manage wrinkles and frown lines.

Botox has been purified though, so the toxin is controlled.

The NHS advises people not to eat food from “bulging or damaged cans”, and to avoid eating off-smelling preserved foods, or those stored at the incorrect temperature or which are out-of-date.

People who make their own preserves should be careful. The spores can grow under low-oxygen conditions, in bottles of oil, for example.

The website for the TV cook Nigella Lawson advises: “Be very careful with homemade flavoured oils, especially those using raw garlic, as there is a risk of botulism.

“The garlic can sometimes pick up botulism from being grown in contaminated soil, and the airless environment of a bottle full of oil gives the botulism an ideal environment in which to thrive.”

Botulism is an emergency. Seek medical help immediately if you or someone you know has symptoms, which can include:

• drooping eyelids
• blurred or double vision
• facial muscle weakness
• difficulty swallowing
• slurred speech
• breathing difficulties

Symptoms usually appear within 12 to 36 hours after eating contaminated food, although it can sometimes be days later.