Does Mouthwash Kill COVID-19?

In June 2020, interest started swirling around mouthwash and its potential effects on SARS-CoV-2, the virus that causes COVID-19. The information initially came from a meta-analysis published in the journal Function. The study posed a theory: since mouthwash can disrupt or damage the outer layer of viruses enclosed by a membrane (called enveloped viruses), mouthwash could have a similar effect on SARS-CoV-2—possibly helping to reduce transmission.

Then in November 2020, mouthwash reemerged in the news with a pre-print (not peer-reviewed) study published on the BioRxiv server, analyzing the effect of common mouthwashes on SARS-CoV-2 in laboratory settings. And this time, researchers from Cardiff University in the UK had some evidence that mouthwash—three common types of mouthwash, to be exact—could kill SARS-CoV-2 in as little as 30 seconds.

Other researchers also had similar findings, showing that several types of mouthwash and nasal rinses "have significant virucidal properties" on coronavirus (virucidal means that it killed the virus). But like the other studies, these were done in vitro, not in humans.

Though it sounded promising, this research didn't mean a lot in terms of stopping the spread of COVID-19, and doctors definitely weren't jumping on the bandwagon to start prescribing a daily rinse to lessen people's chances of catching or transmitting the virus. Here's everything you need to know about mouthwash and coronavirus—and why you shouldn't start stocking up on Listerine.

Can Mouthwash Kill the Coronavirus?

Technically, yes—some types of mouthwash with certain active ingredients have been shown to inactivate SARS-CoV-2 in a laboratory setting that mimicked the conditions of the naso/oropharynx, or back of the throat. The researchers in the unpublished study specifically tested seven different types of mouthwash, including:

• Corsodyl
• Dentyl Dual Action
• Dentyl Fresh Protect
• Listerine Cool Mint
• Listerine Advanced Gum Treatment
• SCD Max
• Videne

The study "demonstrated a wide spectrum of inactivation ability," meaning some were hits and some were misses.

According to the study authors, the two Dentyl products containing cetylpyridinium chloride (CPC), and the Listerine Advanced mouthwash containing ethyl lauroyl arginate (LAE) "eradicated the virus completely after a 30-second treatment."

Other mouthwashes, like Videne containing iodinated povidone, SCD Max, and Listerine Cool Mint containing a mix of ethanol and essential oils, had a moderate effect on the virus. But mouthwashes containing ethanol alone or chlorhexidine (like Corsodyl) didn't have an effect on the virus.

The information gathered from this study suggested that it could be beneficial to test the three types of mouthwash effective in killing the coronavirus in vitro in an in vivo (or in a biologically accurate, possibly human) setting against a live virus load. This way, scientists could determine any potential effects of mouthwash on "reducing the risk of virus exposure within the clinical setting."

Does That Mean Mouthwash Can Protect You From COVID-19?

No one was claiming that what happened in a lab setting could translate to real life—that's why the study authors suggested in vivo testing. The World Health Organization (WHO) said this on the topic: "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 infection."

And even Listerine—one of the mouthwashes tested (and deemed effective) in the new study—says on its website that "Listerine Antiseptic is not intended to prevent or treat COVID-19 and should be used only as directed on the product label.

Although there are recent lab-based reports (in vitro studies) of some Listerine Mouthwashes having activity against enveloped viruses, including coronavirus, there isn't enough available data, and no evidence-based clinical conclusions can be drawn with regards to the anti-viral efficacy of Listerine Antiseptic mouthwash at this time."

Some experts weren't really impressed with the mouthwash-COVID-19 link, either. "It's interesting but this hasn't been studied in real life," William Schaffner, MD, an infectious disease specialist, and professor at the Vanderbilt University School of Medicine, told Health.

"Mouthwash can kill lots of things," added Amesh A. Adalja, MD, senior scholar at the Johns Hopkins Center for Health Security. "It doesn't translate into preventing infection." In fact, Dr. Adalja told Health that it's not terribly hard to kill SARS-CoV-2, on a basic level. "[It's] not a hearty virus," he said, and there are "many substances that can deactivate it."

Thomas Russo, MD, professor and chief of infectious disease at the University at Buffalo in New York, told Health that he's "kind of lukewarm" about the findings. "They're just inactivating RNA in a lab setting as opposed to a real-life setting," he said. "But, if you're already infected, that horse has left the barn."

What he means is that once the virus is actually inside the human body, the damage is already happening by way of replicating in the upper respiratory tract (the nose, sinuses, throat, bronchial tubes, and lungs).

It's also unclear whether this could be used to prevent infection, Dr. Russo said. "The virus can get into your eyes and nasal cavity, too. Once it gets into your cells, would mouthwash really work?" he said. "That remains uncertain."

On the most basic level, Dr. Adalja cautioned about people getting too excited about this. "It's not like you can use the mouthwash, make out with someone, and the risk of contracting COVID-19 is zero," he said.

Do We Know How Mouthwash Could be Used in the Fight Against COVID-19?

That's where this gets especially tricky. "How would you even operationalize this? I don't know that there's a way," Dr. Adalja said. Meaning, you're probably not going to spend your entire day gargling mouthwash—and you shouldn't, he added. "It's also not clear if this would actually decrease infection," Dr. Adalja said.

But Dr. Russo said there's enough evidence to suggest mouthwash could do…something. And, he said, that it's at least worth pursuing with more research. "It would need to be studied in controlled, blinded studies to see if, say, people who regularly use mouthwash are less likely to get infected," he said. Dr. Schaffner agreed. "It probably couldn't hurt," he said.

Experts stress that you shouldn't run out and load up on mouthwash. "These [findings] are all very preliminary," Dr. Russo said.

The information in this story is accurate as of press time. However, as the situation surrounding COVID-19 continues to evolve, it's possible that some data have changed since publication. While Health is trying to keep our stories as up-to-date as possible, we also encourage readers to stay informed on news and recommendations for their own communities by using the CDC, WHO, and their local public health department as resources.