Victorian Chief Health Officer Dr Caroline McElnay said the state's mandatory anaphylaxis notification system had flagged a clear public health hazard. "That's something new for us, and that gives us a signal – it causes concern," she said.
The peptides are being spruiked to teenagers and adults on social media for weight loss, muscle growth, anti-ageing, performance enhancement and cosmetic purposes. Despite repeated warnings from health authorities, the illegal substances are growing in popularity.
McElnay said she had reported the incidents to the federal Therapeutic Goods Administration but suspected the recorded cases were only the tip of the iceberg. "What we're worried about is that these were all linked with unapproved products," she said, noting more people could be suffering milder allergic reactions and not seeking treatment. "The trouble with using a medicine that's unapproved is you really don't know what's in it. It may not be what it says on the label ... the product itself could be contaminated, or there could be varying strength of peptide."
Associate Professor Mark Putland, director of emergency medicine at the Royal Melbourne Hospital, said his health service treated two patients last month who suffered anaphylaxis after using unregulated peptides. The patients, aged between 30 and 50, experienced typical symptoms including breathing difficulties, wheezing, dizziness, hives, abdominal pain and vomiting. Putland said unregulated peptides could trigger anaphylaxis because they were protein-based and had not undergone rigorous safety checks. "The immune system is set up to recognise foreign proteins; it's always recognising invaders," he said. "With the peptides we regulate and use carefully, we'll choose ones that have gone through a safety assessment and don't trigger an immune response."
The recent anaphylaxis cluster follows a separate health alert in June, when six Victorian patients suffered acute liver injuries linked to retatrutide, an experimental weight loss drug not approved for sale in Australia. In New South Wales, there were 1180 emergency department visits linked to unapproved peptide use between July 2025 and September this year.
Melbourne gastroenterologist Dr Darcy Holt said he was treating a growing number of patients who had suffered severe side effects from unregulated peptides. "They are so prevalent, it's normalised," he said. Earlier this year, the nation's Chief Medical Officer Professor Michael Kidd said black market peptides posed a growing public health risk, warning that some products had not undergone sufficient human clinical trials and could cause significant harm.
The TGA has warned that people who advertise, import, manufacture or sell unapproved peptide products face warning letters, fines and criminal prosecutions. In August, the watchdog and NSW Police seized more than $120,000 in illegal peptides and anabolic steroids from two properties linked to a social media influencer. A TGA spokesperson said unapproved peptides had not been evaluated for safety, quality or efficacy. "There is no assurance these products are safe, effective or of acceptable quality," the spokesperson said.