Why You Don’t Want to Clean That Filthy Kitchen Sponge


Your kitchen sponge is meant to clean, but it is a well known fact that these sponges are breeding grounds for all kinds of bacteria.

While the simple solution would be to clean the kitchen sponge, this does not solve the problem. In fact, according to a new study, it might even make it worse.

Credit: YourBestDigs/Flickr, CC BY 2.0

On one cubic inch of a household kitchen sponge, there can be up to 82 million bacteria. According to Dr. Markus Egert of the University of Furtwangen in Germany, “that’s the same density of bacteria you can find in human stool samples. There are probably no other places on earth with such high bacterial densities.”

This alarmingly high number of bacteria are mostly harmless, but there are some more malicious bacteria contained in these everyday items as well. While some may say that all you have to do is clean it, the answer is, unfortunately, not so simple.

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Published in Scientific Reports, a new study has revealed that cleaning sponges actually worsens the situation, causing an even greater growth of harmful bacteria. While placing the sponge in the microwave or boiling it in hot water can kill the less malignant bacteria, the more deadly bacteria continues to grow. With the weaker bacteria gone, the dangerous bacteria expands into its place. In addition, most commercial products did not do much to remedy the situation either. According to the report, “no method alone seemed to be able to achieve a general bacterial reduction of more than about 60%.”

Over 114 sponges were examined for this study, and over 362 different strains of bacteria were found. One of the bacteria pinpointed in the study was Moraxella osloensis. This is the same bacteria that causes dirty laundry to stink, and can account for the odor emanating from kitchen sponges. While it is rare, Moraxella osloensis can cause infections in humans. These are most commonly treated with antibiotics.

Related: 3 Bacteria-Zapping Products for the Home

The state of a kitchen sponge may seem somewhat hopeless, but Egert did come up with a solution for killing bacteria in the most effective manner. He suggests running the sponge through a laundry machine on the hottest setting, using powder detergent and bleach. Instead of allowing it to dry in the kitchen, in which food safety and hygiene is of the utmost importance, the sponge can be left in the bathroom to dry. However, the best solution is to ultimately ditch the sponge after about a week, replacing it with a new one.

Egert remains fascinated by the study, looking to follow it up with a comparison of the best disinfecting methods for sponges. While the laundry machine has been the best bet thus far, he believes there are still options to be discovered, and current myths about sponge cleaning to be busted.

“Now I’m an expert in how to clean sponges,” he told the New York Times. “I’m waiting for the sponge industry to call me.”