The kitchen sponge is one of the germiest things in your home. That's not great for something you use to wipe your plates, glasses and forks. A study has now taken a close look at this hidden germ problem, and it gives some good reasons to replace that wet sponge by your sink more often.
Scientists at the German Federal Institute for Risk Assessment (BfR) tested three common bacteria that can make people sick through food: E. coli, Salmonella and Staphylococcus aureus. They put small numbers of each onto sponges. The bacteria quickly multiplied and stayed alive for at least 14 days, even after the sponges had dried out.
It's hard to say whether this would be enough to make you ill, because that depends on many things. But the researchers say it could be a concern for homes with young children, older people or anyone with a weak immune system.
"Quite a few cases of foodborne infection originate in private households, and they are not always limited to a day or two of feeling unwell," said Andreas Hensel, one of the study's authors.
The germs were also hard to notice. Even when the sponges were full of bacteria, they didn't smell bad or look dirty or greasy. From there, the bacteria can easily spread to a plate you eat from or a board you cut vegetables on.
So should you throw your sponge away for good? Not exactly. The team says the real problem is how people decide when to replace them.
"Many consumers decide when to replace their kitchen sponges based on how they look or smell. However, this is an unreliable indicator," the BfR said.
Instead, think about how you've used it. If a sponge has touched anything that held raw meat, throw it away. Otherwise, you can reduce the bacteria by soaking the sponge in water hotter than 70 degrees Celsius for at least two minutes.
You may also want to stop leaving dirty dishes in the sink overnight. Sinks and tap handles carry some of the most bacteria in a typical home, including E. coli and Staphylococcus. Hygiene experts advise against leaving plates and pans to soak there, which creates a kind of soup for germs.