A Sydney woman is in intensive care and two others are in hospital with suspected cases of botulism linked to unregulated home anti-twist injections.

The case prompted NSW Health to issue an alert urging the community to only receive cosmetic anti-wrinkle injections from authorized practitioners or risk "serious harm and... death".

NSW Police said the 51-year-old woman received an unregulated anti-wrinkle injection at a house in Guildford on January 11.

She was taken to Auburn Hospital on Friday before being transferred to Westmead Hospital, where she was in a stable condition in intensive care on Saturday morning.

A spokesman for the NSW Police Force is working with the Health Care Commission and NSW Health Events, who are investigating the case.

Police said: "Police are cooperating with medical authorities following a complaint to Cumberland Police Command regarding a make-up procedure carried out at a house in Guildford."

Botulinum toxin occurs when toxins attack the body's nerves and cause muscle weakness in the face, mouth, and throat.

NSW Health advises symptoms may appear for up to two weeks and include worsening, difficulty swallowing, drooping eyelids, blurred vision and difficulty breathing.

NSW Health Protection executive director Dr Jeremy McAnulty said the case was a reminder of the potential side effects of unregulated cosmetic injections.

"If cosmetics are used incorrectly, they can cause serious injury or even death in the most serious cases," he said.

"Botulinum toxin, although rare, can be fatal, which is why it is so important that anyone receiving cosmetic injections is supervised by an appropriately registered health practitioner.

"In this particular case, the investigation is continuing but we want people to be aware of the symptoms of botulism as others may have been exposed."

Market researchers Grand View Research rates the Australian facial injection volume industry at $4.3 billion by 2021, with growth expected to exceed 25% annually until 2030.

Injections require a valid prescription from an authorized prescriber such as a physician, but those administering the treatment are not required to complete specific cosmetic injectable material training beyond their general health qualifications. This can include doctors, dentists and nurse practitioners.