Botulinum toxin is the most common non-surgical procedure performed globally, with nearly nine million procedures estimated to take place each year. In the UK alone, around 900,000 botulinum toxin injections are carried out each year.
But with the growing popularity of this procedure comes an increase in risks and unwanted outcomes.
The UK Health Security Agency has recently reported a significant rise in clinically confirmed cases of botulism – a rare illness that can cause symptoms ranging from fatigue, headaches and dizziness to difficulty breathing. Between June 4 and August 6 2025, 41 cases have been confirmed in the UK. These cases appear to be linked to the use of unlicensed products, which are much more potent than licensed versions of the drug.
Botulinum toxin is the most lethal toxin known to man. Even just a small fragment of botulinum toxin – weighing a fraction of the weight of a grain of salt – can be enough to kill a human. This is a key reason why only approved botulinum toxin products should be used, as their ingredients and strength have been carefully scrutinised.
Botulinum toxin is produced by a bacterium called Clostridium botulinum, which is usually found in water, soil and the intestinal tracts of animals. These bacteria can produce seven distinct types of toxins. Only types A and B are used clinically, though botulinum toxin type A is the one most commonly used in cosmetic procedures.
Botulinum toxin acts as a neurotoxin – meaning it impacts nerve function. It specifically inhibits the function of the neurotransmitter acetylcholine which is found in the neuromuscular junction between the nerve and muscle. A variety of nerves use this neurotransmitter – including those involved in key bodily functions such as digestion, breathing and movement.
Botulinum toxin works cosmetically by inhibiting the function of the neuromuscular junction, which paralyses the nerve. This means the muscle doesn’t contract, limiting the overlying skin’s ability to wrinkle. This same function is also the reason botulinum toxin is used to treat eye twitches, chronic migraines, neck spasms, excess sweating, overactive bladder and crossed eyes.
It can take a few days after injection for the full effect of the botulinum toxin to occur. From here, the body begins breaking it down. After around three to four months its effects have fully diminished, which is why follow-up treatments are required.
Botulinum toxin and botulism
As with any procedure, botulinum toxin comes with risks.
The most common side-effects people experience are some initial bruising and swelling and tenderness around the injection site.
But the more concerning side-effect is the risk of botulism. This is a rare complication that can cause symptoms ranging from mild to severe. It isn’t known how common botulism is in people who get botulinum toxin injections, but up to 25% of people who receive cosmetic botulinum toxin injections have complications. Botulism symptoms usually appear the day after receiving botulinum toxin – but in some cases, they can manifest as many as 36 days later.
Mild symptoms include fatigue, headaches, drooping eyelids and visual disturbances. Moderate symptoms involve mild symptoms and difficulty swallowing.
In the worst-case scenario, botulism can lead to anaphylactic shock and respiratory failure. Around 5-10% of untreated botulism cases result in death.
Thankfully, if identified early, treatments are available and effective. But it’s important to note that these treatments cannot reverse any damage that has already been done. They only work to halt further damage. Recovery from botulism can take months.
Botulism can sometimes be mistaken for myasthenia gravis or Guillain-Barré syndrome, two autoimmune conditions that have overlapping symptoms. This is why it’s important to tell your doctor if you’ve had botulinum toxin injections, as there’s no immediate test for the toxin and those tests that show its presence take several days to produce results.
Staying safe
A few key factors can increase your risk of developing botulism from botulinum toxin.
Improper administration increases the likelihood of the botulinum toxin spreading away from the injection site. This increases the risk of experiencing side effects – including botulism.
Exceeding the maximum dose is another factor that increases your risk of botulism. This can happen through basic calculation errors and injecting the wrong amount for the injection site. For instance, men require a higher dose than women due to their increased muscle mass. Not accounting for this could easily result in a dosing error.
Repeated botulinum toxin use can also lead to botulinum toxin resistance, where a patient has built antibodies against the toxin or metabolises the botulinum toxin very quickly. This means they wouldn’t get the required botulinum toxin effect. It may mean that a patient would request a higher dose – potentially above recommended administration levels – to get any effect.
This can be dangerous and also counterproductive as increasing amounts of botulinum toxin runs the risk of increasing antibody production and further reducing the effectiveness of botulinum toxin. It also increases the risk of botulism.
Unlicensed botulinum toxin products also come with the risk of botulism. The recent spike of botulism cases in the UK have been linked to two unlicensed products, Innonox and Toxpia. Both are illegal to supply and use in the UK because their safety hasn’t been assessed by regulatory bodies.
These products also work differently to licensed botulinum toxin products. For instance, Innonox is a “ready-made solution”, which means it can be injected without having to be dissolved in saline. This could lead to an increased risk of dosing errors if a practitioner is not used to the product or switches between using licensed botulinum toxin products and unlicensed ones.
Using a reputable and qualified practitioner is the best way to avoid contracting botulism. They will know how to properly inject botulinum toxin, which dose is safe for you and will only use licensed products that are approved for cosmetic use.
Correction: This article has been updated to replace all mentions of “Botox” with “botulinum toxin”. Botox is a licensed, trademarked product – while botulinum toxin is the generic name for the category of the product. The headline and some of body of the text have also been amended to make clear that this licensed, trademarked product has not been linked with botulism cases in the UK. These cases have only been linked to unlicensed, botulinum toxin products.
Adam Taylor is a Professor of Anatomy at Lancaster University.
This article is republished from The Conversation under a Creative Commons license. Read the original article.
