- Microwaves can kill germs, including viruses and bacteria.
- Research has found that microwaving your sponge for 2 minutes can be an effective way to kill viruses and bacteria.
- However, microwaves aren’t the best disinfectant, and there are better ways to kill germs and viruses in your home.
- This article was medically reviewed by Tania Elliott, MD, who specialises in infectious diseases related to allergies and immunology for internal medicine at NYU Langone Health.
- Visit Insider’s homepage for more stories.
Microwave ovens produce radio-frequency waves that cause the water molecules in an object to vibrate. This vibration causes friction, which allows the object to heat up to a temperature that can kill germs.
That’s why microwaves are sometimes used to disinfect items such as a household sponge, as they are a hotbed for viruses and bacteria.
However, research has found mixed results on whether a microwave can effectively kill germs on a sponge, or even in food. Here’s what you need to know.
Microwaves may be able to kill germs on a sponge
Home microwaves (2.45 GHz) can kill some types of viruses and bacteria within 60 seconds to five minutes, according to the Centres for Disease Control and Prevention (CDC), though more disinfection occurs with higher-powered microwaves.
A 2006 study found that microwaving a sponge at 100% power killed off 99% of the total bacterial count in one to two minutes. The same study concluded that it took 30 seconds to destroy E. coli, a common cause of food poisioning.
In addition, the Environmental Protection Agency (EPA) recommends wetting your sponge and microwaving it every day for two minutes. Ensure the sponge is wet so it doesn’t catch fire and contains no metals so that it doesn’t harm your microwave. You should also keep an eye on the sponge so it doesn’t melt, or start a fire if all the water evaporates.
However, a 2017 study found that, while microwaving can kill bacteria on the sponge, the few that manage to survive may develop resistance. Thus, the researchers recommend replacing sponges on a weekly basis for optimal hygiene.
So while microwaves may not be the best disinfectants, “in general, they would be effective in things like household sponges,” says Tim Landers, an infectious disease expert at Ohio State University College of Nursing.
Microwaves aren’t always effective at killing germs
Other public health experts caution against using sponges for cleaning at all, such as D.T. Simmons, the operations manager from the Florida Department of Health in Franklin & Gulf County. “A sponge is not an ideal cleaning medium,” Simmons says, since it attracts and breeds so many microbes.
Simmons cautions against microwaves to sterilise sponges or food because they don’t fully heat through an object. Ever eaten a frozen meal only to find the middle still cold? The cold spot can be an indicator that the food didn’t get hot enough to kill germs, which the CDC notes is also an issue when using microwaves to disinfect items.
To ensure your microwave has killed off any harmful microbes, use a thermometer to ensure an evenly hot temperature throughout the food. For example, E. coli dies off at 160°F.You should also be sure to stir and rotate food in the microwave so that it heats more evenly.
Overall, Landers and Simmons note that there are better ways to disinfect a kitchen sponge than using a microwave, “like soaking it in a one to 10 diluted bleach solution,” Landers says. “That would be more effective against these kinds of viruses,” especially the novel coronavirus.
Landers also notes to regularly disinfect high-contact surfaces and items, which include doorknobs, keyboards, and countertops, in addition to kitchen sponges. “For disinfection, diluted household bleach solutions, alcohol solutions with at least 70% alcohol, and most common EPA-registered household disinfectants should be effective,” Simmons says.
Related stories about sanitation and keeping clean:
- The best disinfecting cleaners
- How do viruses spread and how to protect yourself against infection
- Beards carry a host of bacteria – but not much more than clean-shaven skin
- What temperature kills germs? How to use heat properly to get rid of bacteria and viruses
- Does UV light kill germs? Getting an at-home sanitizer may be worth it
- Does alcohol kill germs? Yes, as long as the solution is strong enough
- Does vinegar kill germs? It isn’t the best disinfectant for viruses
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