You wipe your kitchen sponge all over the grossest things in your sink, so it makes sense that it would accumulate some pretty gross bacteria. But is it possible to clean or sanitise that sponge? Yes, it turns out — but only as a short-term fix.
Image via Your Best Digs
The Headline: Cleaning a Dirty Sponge Only Helps Its Worst Bacteria, Study Says (New York Times)
The Story: A team of German scientists analysed the bacteria on 14 kitchen sponges, some that were cleaned regularly and some that weren't. The results are interesting to microbiologists but not groundbreaking for the everyday sponge owner. To summarise:
- Kitchen sponges have plenty of bacteria
- None of them are likely to kill you
- After you clean a sponge, it will get dirty again.
When you kill all or most of the bacteria in a germy place, the bacteria move right back in, but sometimes the balance of species is a little different than it was originally: More of one type of bacteria, less another type. That's what they found here (although we have to remember they only studied 14 of the millions of kitchen sponges in the world).
But there's no need to fear these bacteria: Even the "worst" ones the New York Times article mentioned are pretty harmless. None cause diseases in healthy people. Even the one they name checked, Moraxella osloensis, can live happily on your skin without causing problems.
It isn't surprising to find skin bacteria on something you touch with your hands, and it certainly doesn't mean cleaning is useless.
"Please note: we did not directly test any sponge cleaning methods on our own," the study's senior author, Markus Egert, said to me in an email. He doesn't have any data yet on whether one cleaning method is better than another, but he still thinks it's a good idea to clean sponges, and personally prefers throwing them in the washing machine with powder detergent and bleach.
Three other methods that effectively kill bacteria are, according to the Michigan State University extension:
- Microwaving a damp sponge for one minute on high
- Putting it in the dishwasher on the longest and hottest setting (plus dry cycle)
- Soaking it in diluted bleach for one minute
Because the bacterial ecosystem in the sponge changes over time, Egert thinks it's a good idea to retire your kitchen sponge to general cleaning duties (use it in the bathroom, for example) after a while. But we don't have data on how old a sponge is too old for kitchen use, so there's no solid recommendation here.
The Takeaway: Clean sponges will get dirty again, but it's still worth cleaning them.