Phenylephrine is the main decongestant ingredient in soluble and tablet-form cold-and-flu medicines such as Lemsip, Beechams, and Sudafed.

Many popular over-the-counter cold and flu remedies risk being pulled from shelves in the US after its drug regulator ruled a key ingredient to be ineffective.

On Thursday, the Food and Drug Administration (FDA) said oral phenylephrine is not an effective nasal decongestant.

Phenylephrine is the main decongestant ingredient in soluble and tablet-form cold-and-flu medicines such as Lemsip, Beechams, and Sudafed.

It’s meant to work by reducing the swelling of blood vessels in the nasal passages.

Other ingredients, such as paracetamol, help bring down temperatures, and relieve aches and pains.

The FDA said it had come to its conclusion after an “extensive review of available data”.

The ruling does not affect medicines available in the UK, with the Medicines and Healthcare Products Regulatory Agency’s (MHRA) chief safety officer Dr Alison Cave saying there are “no safety concerns” over phenylephrine products and “people can continue to use as directed”.