Yes, you can wash kitchen sponges in the dishwasher, and it’s one of the most effective ways to sanitize them. A USDA-funded study found that running sponges through a dishwasher cycle with a heated dry setting killed 99.9998 percent of bacteria and reduced yeasts and molds to virtually undetectable levels. It’s not quite as powerful as microwaving (which hit 99.99999 percent), but dishwashing outperformed bleach soaking, lemon juice, and plain water by a wide margin.
How to Do It
Place the sponge on the top rack of your dishwasher. Run the hottest, longest cycle available, and make sure the heated dry option is turned on. The water temperature needs to reach at least 155°F during the wash, which most standard dishwashers achieve on their heavy or sanitize settings. The heated dry cycle is essential: it’s not just about the wash itself but the sustained heat during drying that finishes off remaining bacteria, yeasts, and molds.
You can toss the sponge in with a regular load of dishes. There’s no need to run a separate cycle just for the sponge.
Why the Drying Cycle Matters
Sponges hold moisture extremely well, which is exactly what bacteria need to thrive. The USDA research specifically tested dishwashers operating with a drying cycle, and that combination is what produced the near-total bacteria kill. Skipping the dry cycle and pulling out a damp sponge defeats much of the purpose. Research on kitchen cleaning tools confirms that drying is a key factor in reducing bacterial counts, particularly for pathogens like Salmonella. Brushes that were allowed to dry overnight showed significant Salmonella reduction, while tools stored in humid conditions showed none.
Between dishwasher runs, wring your sponge out thoroughly and store it somewhere it can air-dry. Leaving it sitting in a puddle at the bottom of the sink creates the warm, wet environment where bacteria multiply fastest.
Which Sponges Hold Up Best
Cellulose sponges (the classic, slightly stiff ones made from plant fiber) handle dishwasher heat well. They maintain their shape through repeated cycles, dry faster than synthetic alternatives, and don’t shed particles as they break down. That faster drying also means less bacterial growth between cleanings.
Polyurethane foam sponges, the soft, brightly colored type, can tolerate dishwasher temperatures but tend to degrade faster with repeated exposure to high heat. They won’t melt in a standard cycle, but they’ll lose their structure sooner than cellulose. If you’re using a foam sponge, expect a shorter lifespan once you start running it through the dishwasher regularly. Sponges with a coarse scrubbing pad on one side are generally fine as well, though the adhesive between layers can weaken over many cycles.
Dishwasher vs. Microwave
Microwaving edges out the dishwasher slightly on raw kill rate: 99.99999 percent of bacteria versus 99.9998 percent. In practical terms, both methods reduce bacteria to negligible levels. The dishwasher is the better choice if your sponge contains any metal (like embedded scrubbing fibers) or if you’d rather not deal with the risk of a dry sponge catching fire in the microwave. You need to wet the sponge thoroughly before microwaving it, and even then, it comes out scalding hot.
The dishwasher also handles yeasts and molds just as effectively as the microwave. Both methods reduced mold levels to roughly 0.00001 percent of what was present before treatment. Other common methods fall well short. Soaking in a 10 percent bleach solution for three minutes helps but doesn’t match either heat-based approach. Lemon juice and plain water performed the worst of all tested methods.
How Often to Clean and Replace
Bacteria and fungi multiply rapidly in sponges, with lab tests showing significant growth after about 10 days of use. Research published in the Journal of Applied Microbiology found that sponges cleaned in the dishwasher had measurably lower total bacterial counts than uncleaned sponges, confirming that regular dishwasher cleaning does make a real difference over time.
A good routine is to run your sponge through the dishwasher every few days, essentially whenever you’re running a load anyway. This keeps bacterial levels from climbing to the point where your sponge starts to smell sour. That characteristic odor comes largely from Pseudomonas and other bacteria that gradually dominate the sponge’s microbial community the longer it’s in use. Dishwasher treatment is effective at knocking those populations back down.
Even with regular sanitizing, sponges don’t last forever. The physical structure breaks down, creating more crevices for bacteria to hide in, and the sponge becomes harder to fully sanitize. Replacing your sponge every one to two weeks is a reasonable target. If it smells off even after a dishwasher cycle, or if it’s started to fall apart, it’s time for a new one regardless of how recently you bought it.