Can You Microwave A Sponge? Facts, Cleaning Tips, & More

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Can You Microwave A Sponge?

Medically reviewed by Deborah Weatherspoon, Ph.D., MSN — Written by Sarah Kester on August 24, 2021

Does it work?
What's on a sponge?
When to replace
Cleaning tips
Sponge alternatives
Takeaway

For an item that’s supposed to clean your home, sponges are surprisingly dirty. Sponges are a breeding ground for bacteria, including E. Coli and salmonella since they’re typically moist and porous.

While you can throw away a dirty sponge, some try to avoid waste by microwaving it to kill bacteria with heat. But does this purported cleaning hack actually work?

Read on to learn whether you can actually kill bacteria on a sponge by microwaving. We’ll also go over some sponge alternatives that can help you reduce household waste.

Why microwave a sponge?

Microwaving a sponge may seem odd or counterintuitive at first. Here’s some reasons you might want to try it:

You want to kill bacteria. Heat can weaken or kill microscopic colonies of common household bacteria (E.coli, salmonella, and staphylococcus), so heat is purported to help reduce the amount of bacteria on a sponge.
You want to get rid of a musty odor. You may have noticed a lingering odor on the sponge or your hands after using it, and believe that the heat will help reduce or eliminate the odor.
You want to save money. Sponges are designed to be reusable. Some try to extend the life of their sponges by disinfecting them in the microwave instead of buying replacement sponges.

Does microwaving a sponge work?

Microwaving a sponge can kill bacteria.

A 2007 study from the Agricultural Research Service, part of the U.S. Department of Agriculture, found that microwaving a sponge killed 99.9 percent of germs — slightly more effective than throwing a sponge in the dishwasher.

That’s because radio-frequency waves in a microwave cause thermal (heat) and nonthermal (non-heat) effects, causing the water molecules inside a cell to vibrate. The friction associated with this vibration causes increasing levels of heat, which kills the bacteria.

Recent research has also supported this method.

A 2020 study asked 20 participants to use kitchen sponges as normal for 4 weeks. Ten of these participants were instructed to clean their sponges two to three times weekly in a microwave for at least 1 minute at a time at the highest wattage.

The results showed that sponges microwaves for at least 1 minute 2-3 times each week had significantly fewer bacteria than the untreated sponges.

Results can vary depending on the heating setting of your microwave. Certain microwaves may require more time to sufficiently kill bacteria, or may not have wattage high enough to completely eliminate bacteria.

Wet your sponge first

Make sure to wet your sponge before placing it in the microwave. A sponge can ignite and start a fire if it isn’t wet when you microwave it.

What’s on a sponge?

Your sponge can contain several billion bacterial cells in every square cubic centimeter of sponge material — that’s according to a 2017 study in Scientific Reports.

And it’s also likely that a lot of bacteria found on household surfaces and appliances were introduced there by a sponge because many people leave their kitchen sponges wet. Sponges accumulate dirt and bacteria quickly, and leftover food particles are another factor that can also breed colonies of bacteria.

Hundreds of bacteria can live on a sponge, including:

E. Coli may give you an upset stomach and/or diarrhea.
Enterobacter cloacae can cause skin and abdominal infections, among other illnesses.
Klebsiella oxytoca can cause vaginal infections, like a UTI.
Mycobacterium avium can cause pulmonary-related diseases in people with weakened immune systems
Staphylococcus aureus (Staph) can cause a staph infection that results in fever, swelling, and irritated skin.
Salmonella can cause food poisoning.

How long should you use a sponge?

How long you use a sponge depends on use.

If you’re using it every day, consider replacing your sponge at least once a week. If you use a sponge to clean raw food spills, sterilize or replace it right away.

But if you sterilize your sponge regularly, you can likely replace it every 2 weeks without any significant health risks.

Additionally, tap into sensory cues. Consider replacing your sponge if it:

looks dirty
feels slimy
has a foul or abnormal odor

Use different sponges for different jobs

Using different sponges for different areas can also help your sponges last longer.

Use separate sponges for counters, bathroom, and dishes to avoid cross-contamination of bacteria and to allow them to remain dry for longer periods of time. This can help extend their useful lifespan.

What are other sponge-cleaning tips?

There are other effective cleaning methods for both your sponge and other household items that don’t require you to use your microwave.

Use a dishwasher

A 2020 study in the International Journal of Food Microbiologyfound that dishwashing is a highly effective method for reducing bacteria, particularly salmonella.

Alex Varela, owner of Texas-based house cleaning service Dallas Maids, suggests that you should clean your sponges by “placing them in the dishwasher and running the heated dry cycle.”

For best results, put the sponge in the top rack of a dishwasher and wash it with the sanitization cycle.

Use bleach

Bleach is a powerful cleaning agent that kills bacteria and viruses.

To clean your sponges:

Get a small tub and fill it with bleach. The Centers for Disease Control and Prevention (CDC) recommend 1 cup (240 mL) of bleach for every 1 gallon of water.
Place the sponge into the solution to soak for 5 minutes.

Use baking soda and vinegar

Baking soda gets rid of odors and distilled white vinegar will handle bacteria:

Wring your sponge well and leave it to dry overnight.
Sprinkle the softer side of the sponge with a lot of baking soda. If there are two soft sides, you just need to pick one.
Grab a small container and fill it with vinegar so that the sponge is almost covered but not fully immersed.
Carefully place the sponge in the container and keep the baking soda part on top of the bath of vinegar.

Use vinegar

Instead of baking soda and vinegar, it’s also possible to just use vinegar:

Take a dish big enough to hold the sponge and fill it with vinegar.
Soak the sponge in the dish for 5 minutes.
Wring out the vinegar.
Thoroughly rinse the kitchen sponge in warm water.
Let the sponge dry fully.

Are there any effective alternatives to sponges?

Here are some options for a sponge alternative that may be more sanitary or longer-lasting:

Silicone sponge. These are antibacterial and don’t produce microplastics. Silicone sponges are easier to clean because they have flat, sealed surfaces. They’re also eco-friendly since you don’t have to replace them as often.
Handheld dish brush. This tool keeps your hands cleaner and it can be stored upright. This can help it dry faster. Look for brushes whose handles are made from natural materials like finished wood or other compostable products.
Loofah. A natural loofah is made from a gourd in the cucumber family and can be a more sustainable cleaning tool than sponges or other kitchen cleaning tools made with plastic or other manufactured materials.
Sea sponges. These eco-friendly cleaning sponges are naturally found in the sea and aren’t very abrasive.

The takeaway

Putting a sponge in the microwave is a proven way to kill bacteria and germs, reducing waste by allowing your sponge to last longer.

Just be sure to wet the sponge beforehand to avoid any safety hazards and toss any sponges that develop a bad odor or slimy texture.

Consider other, more sustainable cleaning alternatives like silicone or sea sponges to reduce even more waste.

How we reviewed this article:

SourcesHistoryHealthline has strict sourcing guidelines and relies on peer-reviewed studies, academic research institutions, and medical journals and associations. We only use quality, credible sources to ensure content accuracy and integrity. You can learn more about how we ensure our content is accurate and current by reading our editorial policy.

Agriculture research studies. (2007). Best ways to clean kitchen sponges.https://www.ars.usda.gov/news-events/news/research-news/2007/best-ways-to-clean-kitchen-sponges/
Cardinale M, et al. (2017). Microbiome analysis and confocal microscopy of used kitchen sponges reveal massive colonization by Acinetobacter, Moraxella and Chryseobacterium species.https://www.nature.com/articles/s41598-017-06055-9
Cleaning and sanitizing with bleach after an emergency. (2021).https://www.cdc.gov/disasters/bleach.html
Jacksch S, et al. (2020). Metagenomic analysis of regularly microwave-treated and untreated domestic kitchen sponges.https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7284620/
Møretrø T, et al. (2021). Dishwashing sponges and brushes: Consumer practices and bacterial growth and survival.https://pubmed.ncbi.nlm.nih.gov/33152572/
Varela A. Personal interview. (2021).

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Medically reviewed by Deborah Weatherspoon, Ph.D., MSN — Written by Sarah Kester on August 24, 2021

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