The death of a Victorian toddler and cases of four other children who became seriously ill after drinking unpasteurised cow's milk have prompted safety concerns. So what is unpasteurised milk and why are people drinking it?

What is unpasteurised milk?

Pasteurisation is a process that kills harmful bacteria by heating milk to destroy them. The process was first developed by French chemist and microbiologist Louis Pasteur in 1864.

By law in Australia, milk must be pasteurised before it is sold for consumption. During pasteurisation, milk is heated to approximately 72ºC, kept at this temperature for at least 15 seconds and cooled immediately to 4ºC or less. Unpasteurised or "raw" milk has not undergone this process.

Why do people want to drink it?

Some people believe raw milk is more natural and wholesome. They argue that pasteurisation reduces milk's nutritional value and causes lactose intolerance and allergic reactions, although this is disputed by authorities including the US Food and Drug Administration. The FDA says both raw and pasteurised milk can cause allergic reactions in people sensitive to milk proteins. It says pasteurisation "has helped provide safe, nutrient-rich milk and cheese for over 120 years".

What are the dangers of drinking it?

People who drink unpasteurised milk are at risk of acquiring gastrointestinal illness from harmful bacteria including strains of E.coli and listeria. People exposed to these pathogens may experience symptoms ranging from mild gastrointestinal illness including vomiting and diarrhoea, to life-threatening illnesses such as haemolytic uraemic syndrome – which causes kidney failure. Risks associated with drinking unpasteurised milk are greatest for children, the elderly, pregnant women and people with compromised immune systems.

Where are people sourcing unpasteurised milk in Victoria?

The sale of unpasteurised milk for consumption is banned in Victoria due to its health risks. However some raw milk products are being sold in health food stores, labelled as "cosmetic" or "bath" milk, but alongside other drinks and packaged in a similar way to pasteurised milk. Victoria's chief health officer Rosemary Lester says she is concerned about this and has raised the issue with Consumer Affairs Victoria and the Australian Competition and Consumer Commission.