A toxic chemical has been found in counterfeit versions of Sensodyne toothpaste on sale in the UK.
Customers are urged to check the packaging
The affected fake batch is being sold at markets and car boot sales, but not in shops, said the Medicines and Healthcare Regulatory Agency.
The chemical in question, diethylene glycol, can be toxic to children or people with impaired livers or kidneys.
The fake tubes have both English and Arabic lettering, while the real ones use only English in the UK.
Sensodyne's owner, GlaxoSmithKline (GSK), said the authorities had so far seized around 140 of the counterfeit tubes.
"These fake products are illegal and have no connection with GSK," the company said in a statement.
The warning comes just a month after fellow toothpaste company Colgate was hit by a similar problem with dangerous fake products in the US.