MHRA updates botulinum toxin warning after rare botulism cases
The Medicines and Healthcare products Regulatory Agency (MHRA) is strengthening the safety warnings on all UK-authorised botulinum toxin type A products, making the rare risk of treatment-related botulism clearer to practitioners and patients.
The regulator has worked with manufacturers to revise the Summary of Product Characteristics and Patient Information Leaflet for every authorised botulinum toxin type A product, with the updates rolling out over the coming months. The change applies to products used in both cosmetic and medical treatments. In rare cases the toxin can spread beyond the injection site and cause iatrogenic botulism, a serious and potentially life-threatening condition, and the revised wording refers to this risk more explicitly and stresses the need for immediate medical attention. The risk of distant spread has appeared in UK product information since 2007, but it has not previously been set out in these terms.
The MHRA has stressed that this is not a product recall and that no licensed brand or batch has been identified as defective. It is a class-wide strengthening of safety communication, issued alongside a separate warning about the substantially greater risks of counterfeit and unauthorised products.
Symptoms can be delayed, which is central to the updated advice. They typically develop four to eight days after treatment but may take up to four weeks to appear. Warning signs include severe drooping of the upper eyelids, generalised muscle weakness, difficulty swallowing, slurred speech and breathing difficulties, and severe cases can require mechanical ventilation and intensive care. The MHRA says suspected botulism should be treated as a medical emergency, and that anyone experiencing difficulty swallowing, speaking or breathing after treatment should seek immediate help rather than wait for symptoms to pass. Risk is higher in patients with neurological disorders or a history of dysphagia or aspiration, where high doses are given, and where a product is used off-label or injected into an unapproved site.
Going forward, practitioners should confirm that the product being administered is authorised for use in the UK and follow the product-specific instructions for dose, indication and injection site. The MHRA has reiterated that units are not interchangeable between different botulinum toxin products. Prescribers must ensure that anyone they direct to administer the medicine follows the prescription and understands the updated emergency advice, and both new and existing patients should be told about the symptoms of botulism and the four-week risk window. Suspected reactions should be reported through the Yellow Card scheme.
The action follows an outbreak in the summer of 2025. UKHSA recorded 41 clinically confirmed cases of iatrogenic botulism in England between 4 June and 6 August, across the North East, East Midlands, East of England, North West and Yorkshire and Humber. Most of those affected had received products that were not licensed for use in the UK. A separate investigation into 25 cases in North East England found a strong association with an unlicensed product, and testing of seized vials returned a potency of 370 units against a label stating 200, a finding that points to the dosing and quality risks of products sourced outside regulated supply chains.
The MHRA's Criminal Enforcement Unit continues to investigate the illegal sale and supply of unauthorised botulinum toxin. Anyone found selling or supplying unlicensed product faces up to two years in prison and an unlimited fine under the Human Medicines Regulations 2012. For legitimate clinics, the notice reinforces the case for traceable procurement, product-specific dosing, documented consent, clear emergency aftercare information and prompt escalation of any systemic symptoms.
