How to Deep Clean a Stinky Kitchen Sponge

Did you know your kitchen sponge is 200,000 times dirtier than a toilet seat? Yikes! If you’ve been wondering how to clean a kitchen sponge effectively, you’re not alone. While many people try microwaving them to kill bacteria, it turns out this isn’t foolproof—and might even leave dangerous germs behind. So, what’s the safest and most effective way to sanitize your sponge and keep your kitchen safe? Let’s dive in.

“Dear Mary: With all those gazillions of bacteria on kitchen sponges, some say they can be killed off by a minute or two in the microwave. Others say that microwaving is useless to destroy the bad stuff. Do you have a definitive answer on how to clean a kitchen sponge one way or the other?

Many thanks for all your advice and recipes. I’m still reaping raves for your Italian Sausage Vegetable Soup!“

–Pat B., San Gabriel, Calif.

Dear Pat B: This is an important subject. Thanks for bringing it up.

Why Your Kitchen Sponge Smells Worse Than Your Toilet Seat

The poor toilet seat—it’s gotten a bad rap as the dirtiest item in your house. But guess what? It’s not even close to being the worst offender!

Dr. Chuck Gerba, a microbiologist from the University of Arizona, has made it his mission to study how bacteria spreads in our homes. His findings might just make you rethink your cleaning routine. Let’s break it down: the average toilet seat has about 50 bacteria per square inch. Surprising, right?

But hold on, because the real trouble starts in the kitchen. Your cutting board, often exposed to raw meat, is crawling with 200 times more fecal bacteria than your toilet seat. And as shocking as that is, the dirtiest item in your home is likely something you touch multiple times a day—your kitchen sponge.

That innocent little sponge? It’s hosting a staggering 10 million bacteria per square inch. Yes, you read that right—200,000 times dirtier than your toilet seat. And if you think switching to a dishcloth solves the problem, think again—it has about a million bacteria per square inch.

How to Clean a Kitchen Sponge: Microwave vs. Dishwasher

When it comes to figuring out how to clean a kitchen sponge, high heat seems like the obvious solution—or does it? While it’s true that heat can kill bacteria, achieving the temperature needed to sanitize the entire sponge without turning it into a smoldering heap in your microwave is tricky.

Microwave Method

The idea of “nuking” your sponge sounds simple, right? Pop it in the microwave, crank up the heat, and zap those germs away. Unfortunately, it’s not quite that easy. A study reported in The New York Times found that while microwaving reduces bacteria, about 40% of the bad stuff—including potentially harmful pathogens—still survives. And if you leave the sponge in too long? Well, you might end up with a flaming science experiment. Bottom line: the microwave method is unreliable and risky.

Dishwasher Method

Putting that kitchen sponge in the dishwasher daily, or as often as you run a load of dishes, is a much better solution. Between the detergent, high heat, and drying cycle, most bacteria and mildew are destroyed—without the fire hazard.

Let me suggest you don’t rely on just one sponge to do it all. Keep at least two sponges in rotation. While one is in the dishwasher getting sanitized, the other is ready to tackle counters and spills. This way, you’re never left waiting on a clean sponge when you need it most.

DIY Antibacterial Solution for Your Sponge

No dishwasher? No problem! There’s an easy, FDA-recommended way to keep your sponge bacteria-free, and it doesn’t involve shelling out $8 for a fancy bottle of antibacterial cleaner.

Here’s how to make it:

Mix 1 teaspoon of liquid chlorine bleach with 1 quart of clean water in a container or bowl.
Submerge your sponge completely in the solution, ensuring it’s fully saturated.
Let it soak for at least 10 minutes—or even overnight for a deep clean.
Rinse the sponge thoroughly under running water before using it again.

This solution isn’t just for sponges. According to the FDA, it’s also great for sanitizing cutting boards, countertops, and even refrigerator shelves.

Bleach is a powerful disinfectant that’s proven to kill bacteria, viruses, and mildew. It’s especially effective for cleaning porous surfaces like sponges, which tend to trap moisture and germs.

Pro Tips for Better Results

Make a fresh batch of the solution each time you sanitize. Bleach loses its effectiveness when it’s diluted and left to sit for too long.
Use gloves when handling bleach, and work in a well-ventilated area to avoid harsh fumes.
Have multiple sponges in rotation so you always have a clean one on hand while another is soaking.

Alternatives to Traditional Sponges

If the idea of billions of bacteria lurking in your sponge makes you cringe, consider switching to cotton or microfiber cloths. These reusable options are less likely to harbor germs, dry faster, and can be tossed in the laundry after each use. They’re durable, multipurpose, and far easier to keep clean than a sponge.

Stock up on a few cloths so you can rotate them throughout the week. After each use, rinse them thoroughly and let them air dry before tossing them into the laundry. Wash them in hot water with detergent, and avoid fabric softener—it can reduce their cleaning effectiveness.

Unlike sponges, which hold onto moisture (and germs), microfiber cloths dry quickly, minimizing bacteria growth. Use them for wiping counters, scrubbing dishes, or even cleaning glass and mirrors without leaving streaks.

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Still Attached to Sponges?

If you can’t imagine life without a sponge, don’t worry. The key is regular replacement. Aim to swap out your sponge every week, and sanitize it between uses to keep bacteria levels in check. Whether you stick with sponges (and replace them often) or switch to cloths, the goal is the same: a fresh, germ-free kitchen.

Hope that helps, Pat B. Keep up the great work with your soup—sounds like a dish your guests won’t forget anytime soon!

Question: What’s your go-to method for keeping your kitchen sponge clean? Are you Team Microwave, Team Dishwasher, or something else?

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Jaye says:

January 23, 2025 at 1:34 pm

I wash and dry the kitchen sponges with the load of kitchen dishcloths and towels. Hot water and hot dry. I do not cross contaminate and wash all fequently. No stink and works great. Sponges hold up for ages. Has worked for our family for 40 years.

Lija Wills says:
January 26, 2025 at 1:05 pm

Jaye, I do the same except I’ve never dared to put them into the dryer. Are you saying that the sponges don’t degrade in the dryer? I’ve always let them air dry but I like the idea of using a dryer better because it sounds more sanitary. I just didn’t think plastic sponges would hold up in a dryer. Maybe you’re using a different quality of sponge? Could you elaborate for me please? I’m interested.

linda says:

January 23, 2025 at 1:31 pm

i don’t use a sponge on anything that comes in contact with food. i use it to clean counter tops, the table, cabinets, the outside of the fridge, stove and dishwasher. i soak it in vinegar and nuke it once a week. none of us have died yet.

Lilia says:

November 3, 2023 at 4:39 pm

I boil 3 cups of water every morning. I use one cup to make a cup of instant coffee to drink with breakfast and pour the rest of the boiling water on my kitchen sponge to kill the bacteria. I do this every morning. After a month or so, I use a new sponge and use the old sponge to clean my counter tops, kitchen sink or walls. After reading the previous posts about how good the Swedish dishcloths are, I will definitely order some.

Mary Hunt says:
November 6, 2023 at 8:32 am

I wouldn’t depend on that cup of boiling water, Lilia According to this study, boiling water—even putting it into a pot of boiling water—is an ineffective as putting it in the microwave oven. You won’t make it cleaner and it may even promote the growth of certain types of bacteria.

Susan M Sharp says:

October 18, 2023 at 10:36 am

The first time I used a sponge in the kitchen and smelled the funk was the last time I used a sponge. I use a dishcloth, lately the Swedish dishcloths. They are miraculous and with a good rinse and wring out they’re ready to go. No stench.

Jeannie says:
October 18, 2023 at 2:43 pm

I switched to Swedish dishcloths a few months back and love them. I now give them as gifts!

Robyn says:

October 17, 2023 at 8:59 pm

I love my microfiber sponges. They wash up beautifully, last a long time, and cost about the same as a five pack of large yellow and green scrubber sponges.

Pat A Weiser says:

October 17, 2023 at 8:11 pm

We don’t have a dishwasher, except for my husband. What should those of us without a dishwasher do?

Mary Hunt says:
October 17, 2023 at 10:13 pm

Another option, espeically if you don’t have a dishwasher is to soak that daily sponge in a good antibacterial sanitizer for at least an hour up to overnight. But don’t spend $8 for a 16-oz. bottle from the store. Make it yourself for pennies!

According to the FDA, one teaspoon of liquid chlorine bleach per quart of clean water can be used to sanitize all kitchen surfaces like cutting boards, counter tops, refrigerator shelves—and sponges!

Lisa says:

October 17, 2023 at 7:03 pm

While we are at it, can we roast the seeds at the same time? Or is there a different time and temp? What sort of prep do they need? Thanks for all you do! Always learn alot.

Mary Hunt says:
October 17, 2023 at 10:17 pm

Please follow the guidelines at EverydayCheapskate.com/contact to submit an off-subject question. Thanks!

Claudia says:

October 17, 2023 at 5:31 pm

How do I clean terrazzo floors that have yellowed pathways worn into them?

Mary Hunt says:
October 17, 2023 at 10:16 pm

Please follow the guidelines at EverydayCheapskate.com/contact to submit an off-subject question. Thanks!

Sue says:

October 17, 2023 at 4:37 pm

My solution to bacteria-laden sponges? Throw them away and never buy them again. As Mary suggested a dish cloth, microfiber or whatever can be thrown in the wash (hot water) after one or two uses which is what I do.
Sponges don’t pick up as much as a dish cloth and the bacteria that a stinky sponge harbors cannot be rinsed out.
Just my opinion.
Thanks so much for all you do, Mary! ❤️

Why Your Kitchen Sponge Smells Worse Than Your Toilet Seat