New research out of Pennsylvania found that certain oral antiseptics and mouthwashes can inactivate human coronaviruses similar to the novel coronavirus.
The findings add to several other studies that produced similar results, suggesting some of these products might work against SARS-CoV-2 by reducing the amount of virus in infected individuals.
But no studies to date have tested how rinses actually interact with the novel coronavirus inside a person’s mouth; all of them have been confined to controlled laboratory settings.
So, while some experts say this readily available tool can help reduce the spread of COVID-19, others say there’s virtually no evidence to tell if that’s the case.
“There is potential for mouthwash with alcohol to reduce, maybe slightly, short-term spread of virus to close household contacts. The alcohol might kill virus in the mouth surfaces temporarily — so might a shot of whiskey, rum or tequila,” Dr. Eric Bortz, an assistant professor of biology who’s studying SARS-CoV-2 at the University of Alaska Anchorage, told Healthline.
“But that doesn’t mean you should use it as a first line of defense. For example, bleach kills virus — but don’t drink it or wash your mouth with it because it might kill you too!” Bortz said.
That’s because the coronavirus is continuously producing more copies of itself in your throat, nose and upper and lower respiratory tissues, experts say. This means the virus could already be replacing itself in your mouth as you rinse — and it will continue to do so until your body has developed antibodies against the virus.
“So for most people with coronavirus, mouthwash will be of limited value in preventing [it’s] spread,” Bortz added.
The Penn State College of Medicine Research mixed a strain of human coronavirus that was not SARS-CoV-2 into solutions of baby shampoo — often used by doctors to cleanse the sinuses — various peroxide antiseptic rinses and several brands of mouthwash, according to a news release.
They let the virus sit there for 30 seconds, one minute and two minutes before putting the solutions in contact with cultured human cells. The team then counted how many cells were alive after several days of exposure. All of them inactivated 99% of the virus.
However, the researchers note clinical trials are needed to test if mouthwash has a significant enough effect to reduce viral spread. “Even if the use of these solutions could reduce transmission by 50%, it would have a major impact,” study lead author Craig Meyers said in the news release.
A separate study published in June found that mouthwash with just 0.5% concentration of povidone‐iodine, a common disinfectant, “rapidly inactivated” the novel coronavirus in a test tube.
But in an infected individual’s mouth, the response may be different. That’s because mouthwashes are designed to kill 99.9% of germs that cause bad breath, plaque and gingivitis, according to Listerine — not coronaviruses.
The company says their mouthwash “has not been tested against any strains of coronavirus. Only some LISTERINE® mouthwash formulations contain alcohol, and if present is only around 20% alcohol.”
“There might be some scenario where you might get SARS-CoV-2 in your mouth and then use mouthwash, which might kill it,” Dr. John Sellick, an infectious disease expert and professor of medicine at the University at Buffalo/SUNY, told Shape. “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.”
The World Health Organization has also said there’s no evidence mouthwash can prevent coronavirus infection or get rid of it.
“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],” the WHO said.
Experts say it’s still unclear how the coronavirus hops from one body part or system to another, although they do know some of the main points of entry are the nose, eyes and mouth. So, using rinses to kill SARS-CoV-2 in your mouth could really only work if you’ve gargled the product before the virus infects your other cells — timing that no one fully understands.