Experts explain what mouthwash can and can't do to reduce the spread of COVID-19.

By Korin Miller
October 14, 2020
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Like most people, you've probably stepped up your hygiene game over the past few months. You wash your hands more than ever, clean your place like a pro, and keep hand sanitizer nearby when you're on the go to help prevent the spread of coronavirus (COVID-19). Given that you're on your cleanliness A-game, you may have seen reports suggesting that mouthwash can kill SARS-CoV-2, the virus that causes COVID-19, and wondered what that was all about.

But wait — can mouthwash kill the coronavirus? It's a little more complicated than you'd think, so here's what you need to know.

Where did the idea of mouthwash killing coronavirus come from?

There's actually some early research to suggest that this might be a thing. A scientific review published in the scientific journal Function analyzed whether mouthwash could have the potential (emphasis on "could") to reduce transmission of SARS-CoV-2 in the early stages of infection. (Related: Everything You Need to Know About Coronavirus Transmission)

Here's what the researchers laid out: SARS-CoV-2 is what's known as an enveloped virus, meaning it has an outer layer. That outer layer is made up of a fatty membrane and, the researchers point out, there's been "no discussion" so far about whether you could potentially practice "oral rinsing" (aka use mouthwash) to damage this outer membrane and, as a result, inactivate the virus while it's inside an infected person's mouth and throat.

In their review, the researchers looked at previous studies that suggest that certain elements commonly found in mouthwashes — including low amounts of ethanol (aka alcohol), povidone-iodine (an antiseptic often used for skin disinfection before and after surgery), and cetylpyridinium chloride (a salt compound with antibacterial properties) — could disrupt the outer membranes of several other types of enveloped viruses. However, it's not known at this time whether these elements in mouthwash could do the same for SARS-CoV-2, specifically, according to the review.

That said, the researchers also analyzed existing mouthwashes for their potential ability to damage SARS-CoV-2's outer layer, and they determined that several should be investigated. "We highlight that already published research on other enveloped viruses, including [other types of] coronaviruses, directly supports the idea that further research is needed on whether oral rinsing could be considered as a potential way to reduce transmission of SARS-CoV-2," the researchers wrote. "This is an under-researched area of major clinical need."

But again, it's all theory at this point. In fact, the researchers wrote in their review that they still aren't sure how, exactly, SARS-CoV-2 moves from the throat and nose to the lungs. In other words, it's unclear whether killing (or even damaging) the virus in the mouth and throat with mouthwash would have any effect on not just transmission, but also the severity of the disease if and when it potentially begins affecting the lungs.

Lead study author Valerie O'Donnell, Ph.D., a professor at Cardiff University, tells Shape that clinical trials are underway to dive deeper into the theory. "We hope there will be more answers soon," she says.

So, can mouthwash kill COVID-19?

For the record: There is currently no data to support the notion that mouthwash can kill SARS-CoV-2. The World Health Organization (WHO) says as much, too: "Some brands of mouthwash can eliminate certain microbes for a few minutes in the saliva in your mouth. However, this does not mean they protect you from [COVID-19] infection," reads an infographic from the organization.

Even Listerine says in an FAQ section on its website that its mouthwash "has not been tested against any strains of coronavirus."

To be clear, that doesn't mean mouthwash can't kill COVID-19 — it just hasn't been tested yet, notes Jamie Alan, Ph.D., an assistant professor of pharmacology and toxicology at Michigan State University. "Although some mouthwashes contain alcohol, it's usually less than 20 percent, and WHO recommends greater than 20 percent alcohol to kill SARS-CoV-2," says Alan. "Other alcohol-free mouthwash formulations contain salt, essential oils, fluoride, or povidone-iodine, and there is even less information" on how these ingredients might affect SARS-CoV-2, she explains.

While many brands of mouthwash brag that they kill a large portion of germs, "what they're really made for is to kill the bacteria that give you bad breath," adds John Sellick, D.O., an infectious disease expert and professor of medicine at the University at Buffalo/SUNY. If you use mouthwash consistently, you're "hitting bacteria on the surface and knocking them down a bit," he explains. (Related: 'Mask Mouth' Might Be to Blame for Your Bad Breath)

But, as for SARS-CoV-2, there is only minimal data to suggest this is a thing. Research published in the Journal of Prosthodontics analyzed mouthwashes containing various concentrations of povidone‐iodine and found that a mouthwash with just a 0.5 percent concentration of povidone‐iodine "rapidly inactivated" SARS-CoV-2 in a lab setting. But, it's important to point out that these results were found in a controlled lab sample, not while being swished around in someone's mouth IRL. So, it's difficult at this point to make the leap that mouthwash can kill COVID-19, according to the research.

Even if research does eventually show that certain forms of mouthwash can kill COVID-19, Dr. Sellick says it would be hard to say how useful that might be outside of something like protecting your dentist during a dental procedure. "There might be some scenario where you might get SARS-CoV-2 in your mouth and then use mouthwash, which might kill it," he explains. "But I would be surprised if it had any effect. You would have to have a continuous infusion of the mouthwash, even if it did kill SARS-CoV-2." You'd also need to catch the virus before it infected other cells in your body (the timing of which is also super unclear in this context), adds Alan.

Can mouthwash kill other viruses?

"There is some evidence," says Alan. "There have been some studies that show that mouthwashes that contain around 20 percent ethanol can kill some, but not all viruses." One 2018 study published in the journal Infectious Diseases and Therapy also analyzed how well a 7 percent povidone-iodine mouthwash (as opposed to an ethanol-based mouthwash) performed against oral and respiratory tract pathogens. Results showed that the mouthwash "rapidly inactivated" SARS-CoV (the coronavirus that spread around the world in 2003), MERS-CoV (the coronavirus that made waves in 2012, particularly in the Middle East), influenza virus A, and rotavirus after just 15 seconds. Much like the more recent Function study, however, this type of mouthwash was only tested against these pathogens in a lab setting, rather than in human participants, meaning the results might not be replicable IRL.

Bottom line: "The jury is still out" on how mouthwash might affect COVID-19, says Alan.

If you're interested in using a mouthwash anyway, and you want to hedge your bets on its coronavirus-protecting properties, Alan recommends looking for a formula that contains alcohol (aka ethanol), povidone‐iodine, or chlorhexidine (another common antiseptic with antimicrobial properties). (Related: You Need to Detox Your Mouth and Teeth — Here's How)

Just keep this in mind, says Dr. Alan: "The alcohol content can be irritating to the mouth [but] this is probably the most likely over-the-counter form that has the best chance at killing germs."

The information in this story is accurate as of press time. As updates about coronavirus COVID-19 continue to evolve, it’s possible that some information and recommendations in this story have changed since initial publication. We encourage you to check in regularly with resources such as the CDC, the WHO, and your local public health department for the most up-to-date data and recommendations.

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