Skip to content

How dirty is your kitchen sponge?

    Clean Dishes with a Clean Sponge

    person washing sink fill of dishes

    When we do the dishes, we generally wring out the kitchen sponge after use. But we’ve all lived with roommates or family members who do the opposite. They wash their dishes and drop the sponge in the bottom of the sink, where it sits in a puddle and never fully dries out.

    Sponges have lots of little crevices and tend to be both warm and wet, an ideal environment for bacteria to flourish. So we were curious: Are those soggy sponges harboring more bacteria than sponges that we wrung out after use? We decided to find out.

    Doing the dishes might be one of the most hated household chores in the country. Surprisingly it’s possible to make that seemingly endless task even worse. Even when you’ve finally emptied your kitchen sink of every last mug, fork, and pot that’s been “soaking” there for days, there’s one major germ source still lurking in your kitchen: drumroll please, it’s the sponge.

    This however isn’t an excuse to lean into your food delivery habit. Instead lean into adulting by learning how to clean your sponge properly. With our help, you can actually keep your dishes as clean as they were the day they came out of their box.

    Does your wet kitchen sponge breed bacteria? 

    In one of our case studies, we partnered with a local lab where we used six identical sponges to clean up dishes, carefully measuring the amount of food, as well as the temperature of the water and the amount of soap we used. After each use, we squeezed the water out of three of the sponges and placed them in a dish rack so they could air-dry. We left the other three wet and set them in open plastic bowls, mimicking sponges that had simply been dropped and left in a damp place such as the bottom of the sink. After the two weeks, an independent lab measured the total bacterial count of each sponge in colony-forming units per milliliter (CFU/mL)—and the difference was staggering.

    The sponges that had been left wet averaged more than 500,000 CFU/mL, while the wrung-out sponges came in at just 20 CFU/mL. The lab did not differentiate species of bacteria, so we don’t know if any of this bacteria was potentially harmful. But the conditions for growing good bacteria and bad bacteria are the same, and the results were clear: Wet sponges really do harbor more bacteria.

    Methods to sanitizing your sponge properly

    person holding a blue sponge over a stainless steel kitchen sink 

    Usually, we wring out sponges and store them in a place where they can dry between uses. But even a clean kitchen sponge can still get grimy. Worse, it can stay damp on the inside even when it looks and feels dry on the outside.

    To learn how to clean them, here are methods you can follow:

    • METHOD 1: Dampen your sponge and microwave it for at least 2 minutes.
    • METHOD 2: Run your sponge through your dishwasher on a setting that reaches at least 155 degrees and has a heated dry cycle (sometimes called sani-rinse, sani-wash, or sanitation cycle), preferably every time you run your dishwasher.
    • METHOD 3: Submerge your sponge in a bleach solution (¾ cup of bleach for every gallon of water) for at least 5 minutes and then rinse it thoroughly.

    After using any of these methods, allow the sponge to dry completely before using it again, ideally in a dish rack or a container that allows air to circulate around all surfaces of the sponge.

    Will it really kill all the bacteria?

    A good rule of thumb is to replace your sponge every one to two weeks, cleaning it regularly in between uses, and storing it someplace where it can dry.

    The experts we spoke to insisted that regularly cleaning a sponge is essential. But it’s not going to remove every bit of bacteria or make your sponge last forever. Some studies show that these methods are effective, while others indicate that they remove no more than 60 percent of bacteria. At home, there’s just no way to know how much bacteria was on your sponge to begin with or how much has been killed. Neither at-home sanitization method will dramatically extend the life of your sponge. A good rule of thumb is to replace your sponge every one to two weeks, cleaning it regularly in between uses, and storing it someplace where it can dry.

    The health risks of dirty kitchen sponges

    6 dirty blue sponges on a black countertop

    The biggest issue here—and where a lot of the bacteria comes from—is that your sponges are responsible for doing multiple jobs and cross-contamination is a huge risk.

    Many people use the same sponge to wash dishes as they do for cleaning up a counter after meal prep, which means you’re using the same tools to clean up raw (and potentially dangerous) food remnants as you are to scrub your plates and bowls. And yes, all this bacteria can potentially make you sick.

    We’re talking E. coli and salmonella, two super common foodborne illnesses, but also Campylobacter, which causes an estimated 1.3 million illnesses each year in the U.S. and is the leading cause of bacterial diarrhea.

    When should you replace your sponge?

    Like rolls of toilet paper, tubes of mascara, and pairs of running sneaks, you’ll go through many sponges in your lifetime. So accept now that each will be just a temporary part of your kitchen.

    Trust that your nose will know when it’s time to throw out a sponge. If it starts to smell, shows noticeable wear, or just isn’t working anymore, it’s time for it to go. And for you to move on to a bigger, better, and cleaner sponge.

    You and your dishes will be glad you did.

    Cleaning your home is not as straightforward as it is. Sometimes, the bigger picture in cleaning is just the first step. To ensure a healthy home, even the state of your kitchen sponges are critical. For this reason, hiring cleaning service professionals can help keep your home or office clean at all times. Contact us to get a free quote today.