Can You Get Botulism From Pesto?
Pesto has been responsible for botulism poisoning in the past. However, the better food safety standards we have nowadays ensure that 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 harmful in themselves. 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 put 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. You cannot detect these toxins by sight or smell.
Why is pesto susceptible to botulism?
Because garlic and oil are vital ingredients in most pesto sauces, producers take mitigating the risk of botulism exceptionally seriously. Thankfully, the UK has incredibly high food safety standards, and the risk of contracting botulism from 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, unless you are 100% confident that you understand the science, making pesto that can be stored at room temperature for many months is best left to the professionals. 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
Pesto producers ensure no botulism risk by ensuring their sauces are acidic and heat-treated. (Some producers use preservatives, too, although that is not strictly necessary.)
Botulism spores cannot produce toxins in acidic environments, so if companies ensure that the pH of their sauces is below 4.6, the chances of getting botulism poisoning from pesto are 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, refrigerate it and eat within five days.
Some notable instances of botulism poisoning from pesto
2024
Botulism toxins in a wild garlic pesto hospitalised five people in France. A small artisan brand, O'Ptits Oignons, produced 600 jars of the contaminated pesto, sold at a farmer's market in the Indre-et-Loire region. The five affected individuals had consumed the pesto at the same birthday party. Authorities quickly instructed anyone who had purchased 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 multiply rapidly.
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 hospitalised, though thankfully, both made a complete recovery. An investigation found that the pesto producer 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 get early treatment. Symptoms often start with vomiting and diarrhoea but can quickly turn into blurred vision, slurred speech, and difficulty breathing.