Listeria and ice cream: who should be careful

Listeria survives freezing, and a small dose is enough to make vulnerable people ill. What outbreaks in the US and the UK showed, and who should take more care with ice cream.

Salmonella and eggs are often talked about. Less well known is the bacterium Listeria monocytogenes, which is particularly troublesome for ice cream: it tolerates both cold and freezing. For most healthy people it isn’t a major risk, but for some groups it can be dangerous. This article explains why, and how to avoid it at home.

Why listeria is different

Most bacteria that cause food poisoning hardly multiply in the fridge. Listeria does. According to the textbook by H. D. Goff (University of Guelph), it grows even at refrigeration temperatures, and freezing doesn’t destroy it – it survives in ice cream and is still alive after thawing. Goff also points out that in vulnerable people a very small number of viable cells is enough to cause illness.

Heating the mix (pasteurisation) kills listeria. The problem therefore usually arises not during cooking but after it – when the bacterium gets into the finished mix from the machine, pipes, containers or the environment. Goff calls this stage post-pasteurisation contamination and considers thorough sanitation the only protection against it.

Did you know?

According to the European Centre for Disease Prevention and Control (ECDC) and EFSA, listeriosis had the highest rate of hospitalisations and deaths of all foodborne illnesses in the EU in 2024: about 7 in 10 of those ill were hospitalised and roughly 1 in 12 died.

What ice cream outbreaks have shown

US 2015

In 2015 there was a listeria outbreak in the US linked to one manufacturer’s ice cream, with 10 cases. A scientific analysis published in 2016 in the journal Emerging Infectious Diseases (Pouillot et al.) focused on patients in a hospital in Kansas. They were people over 67 in poor health who had drunk milkshakes made with the contaminated ice cream in hospital.

What was surprising was how low the contamination was: from 0.12 CFU (colony-forming units) per gram up to hundreds of CFU per portion. The estimated dose per milkshake averaged about 1,240 cells. For a healthy person this would probably have had no effect, but for frail patients it was enough.

UK 2024–2025

According to a 2025 report by Food Safety News, the UK authorities investigated an outbreak linked to frozen desserts supplied to hospitals. There were 5 confirmed cases and 3 deaths, and the median age of those ill was 87. Listeria was found in the desserts even though it was below the limit of 100 CFU per gram. The information comes from a press report, not directly from an official publication.

OutbreakCasesWho fell illContamination
US 201510mainly older hospital patientsvery low (from 0.12 CFU/g)
UK 2024–255, of whom 3 diedhospital patients, median age 87below the limit of 100 CFU/g

What both cases have in common is that the ice cream or dessert reached people in hospital, and that even a small number of bacteria was enough.

Limits in the EU

Microbiological criteria for food in the EU are set by Commission Regulation (EC) No. 2073/2005. For ready-to-eat foods (including ice cream), the limit for listeria is 100 CFU per gram. For ice cream the regulation also monitors salmonella and Enterobacteriaceae bacteria as an indicator of production hygiene. The exact wording of the row for ice cream should be checked in the text of the regulation – we weren’t able to load it in full during our research.

The UK case shows that even meeting the limit may not be enough for the most vulnerable people.

Who should be more careful

Listeriosis is particularly dangerous for these groups:

  • pregnant women,
  • older people, especially those in poor health,
  • people with weakened immunity.

Warning

If you belong to a vulnerable group, avoid ice cream from uncertain sources (a stall with no visible hygiene, ice cream of unknown origin) and ice cream made from unpasteurised ingredients. Ask your doctor about what is suitable for you.

How to reduce the risk at home

  1. Use pasteurised milk, cream and eggs, or heat the mix thoroughly.
  2. Cool the mix quickly after heating and work with clean utensils. Listeria most often gets into the mix after cooking.
  3. Take the ice cream maker apart and wash it after every use, then let it dry. You’ll find the details in the article on keeping your ice cream maker clean.
  4. Use the mix within 48 hours and don’t put leftovers back.
  5. Don’t refreeze melted ice cream. Listeria survives freezing and has time to multiply while the ice cream is melted.
  6. Wash fruit and herbs for ice cream thoroughly. Freezing won’t disinfect them.

Tip

For vulnerable members of the family, make ice cream in small batches and serve it fresh, ideally on the day it’s made.

Summary

  • Listeria grows in the cold and freezing doesn’t kill it.
  • Heating the mix kills it – the risk only comes afterwards, via unclean utensils and surroundings.
  • A small dose usually won’t harm healthy people, but it can harm vulnerable groups.
  • Pasteurised ingredients, a clean machine and fresh ice cream are the best protection.

Sources

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