Can You Get Botulism From Pesto?
In the past, pesto has been responsible for botulism poisoning. However, the better food safety standards that we have nowadays ensures outbreaks are vanishingly rare and tend to only come from amateur producers who don't understand the science behind preventing botulism spores from producing toxins.
What exactly is botulism?
Clostridium botulinum spores are found on the surfaces of most fruits and vegetables, although they are not in themselves harmful. Under certain conditions, though, these spores can start to produce a highly toxic poison that, if consumed, can lead to paralysis and, in the most extreme circumstances, death.
Botulinum bacteria thrive in alkaline, anaerobic environments. If you were to put some garlic cloves (or any root vegetable) into a jar of oil and leave it on your kitchen worktop for a few days, you would have inadvertently created the perfect breeding ground for botulism toxins to thrive. Neither sight nor smell can be used to detect these toxins.
Why is pesto susceptible to botulism?
Because garlic and oil are key ingredients in most pesto sauces, mitigating the risk of botulism is something that producers take extremely seriously. Thankfully, here in the UK we have incredibly high food safety standards, and the risk of contracting botulism from a shop-bought pesto is virtually zero.
It’s easy and safe for anyone to make fresh pesto at home. In fact, we actively encourage it! However, when it comes to making pesto that can be stored at room temperature for many months, it’s best left to the professionals unless you are 100% confident that you understand the science. In well-meaning but ill-educated hands, the combination of garlic and oil can represent a genuine danger to your health.
How to prevent botulism poisoning from pesto
The way pesto producers ensure there is no risk of botulism is by ensuring their sauces are both acidic and heat-treated. (Some producers use preservatives too although that is not strictly necessary.)
Botulism spores cannot produce toxins in acidic environments, so providing companies ensure that the pH of their sauces are below 4.6, the chances of getting botulism poisoning from pesto is vanishingly small.
When it comes to consumers mitigating the risk of botulism poisoning, the most important thing is to store your shop-bought pesto correctly. Always store your jar according to the manufacturer's instructions and never allow it to go past its use-by date. Once opened, pesto must be refrigerated and eaten within 5 days. It should be stored in a way that avoids any risk of cross-contamination from other items in your fridge.
Some notable instances of botulism poisoning from pesto
2024
Five people were hospitalised in France after eating a wild garlic pesto that contained botulism toxins. 600 jars of the pesto were produced by a small artisan brand called O'Ptits Oignons and sold at a farmer’s market in the Indre-et-Loire region of France. The five people had all attended the same birthday party where the pesto was served, and the authorities were quick to instruct anyone else who had bought a jar to dispose of it immediately.
2023
A Brazilian woman had to spend almost a year in hospital after eating what she described as “delicious” pesto. The jar that she bought from her local supermarket had no expiration date or storage instructions and doctors believe that storing it at room temperature meant harmful botulism toxins were able to rapidly multiply.
2014
A father purchased several jars of pesto at a Californian farmer’s market and gifted his daughter a jar which she ate with her best friend a few days later. They started experiencing botulism symptoms within around 24 hours and were immediately hospitalised, though thankfully both made a complete recovery. An investigation found that the producer of the pesto was working from unregistered premises and was unaware that her sauces must be acidic to prevent botulism spores from producing dangerous toxins.
Botulism symptoms
According to the NHS, 5-10% of all botulism cases are fatal, meaning it is critical to recognise the signs and getting early treatment. Symptoms often start with vomiting and diarrhoea but can quickly turn into blurred vision, slurred speech, and difficulty breathing.