Kitchen sponges have gotten more bad press than R. Kelly—and are rumored to be almost as unsanitary. Some studies—and there is a surprisingly vast amount of scientific literature devoted to this humble kitchen cleaning product—have compared the bacterial activity in the average pot scrubber unfavorably with that of a toilet seat. Other research, however, reported relatively few pathogens on sponges, and that some of them may even help scientists figure out how to fight antibiotic-resistant bacteria.
Most germ experts agree that yes, kitchen sponges do tend to harbor pathogens (they’re moist, porous, and come into contact with the grimiest places in your kitchen), and if you keep them longer than a week or two, it’s a good idea to clean them to avoid spreading those nasties around.
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But disinfecting a sponge is also a breeding ground for debate. Is blasting germs with heat more effective than dousing them with chemicals? Manan Sharma, PhD, a research microbiologist with the Environmental Microbial & Food Safety Lab at the USDA, conducted a study comparing several popular methods: microwaving, running it through the dishwasher, and soaking it in bleach or lemon juice.
“Methods that provide heat—microwaving, or placing sponges in a dishwasher cycle that has a heated dry—are probably the best ways to disinfect sponges,” he concluded. He personally uses the dishwasher method, which proved the most effective in the study for lowering counts of bacteria, yeast, and mold, and is safe for sponges with metal or metal fibers in them, unlike a microwave. (Though there have been independent accounts of sponges going rogue and clogging the dishwasher drain.)
Nuking was the second-best method, though Sharma cautions that you want to make sure the sponge is damp so it generates bacteria-killing steam, and use caution afterward since the sponge will be hot to the touch.
While popping your sponge in the dishwasher regularly will extend its life (roughly 1 in 5 people wait three to four weeks before tossing a sponge; 1 in 10 hold out a month or longer, according to the Academy of Nutrition and Dietetics, and that was all before the Scrub Daddy), a more important takeaway may be this: Use separate sponges for cleaning dishes and cleaning up spills, and use paper towels for raw meat juices. (Some experts even recommend tea towels over sponges because they can be swapped out and washed more regularly.) That can limit cross contamination better than any disinfecting procedure.
