They found that some nasal rinses and mouthwashes might be able to inactivate some human coronaviruses, thereby decreasing the spread by reducing the “viral load” we put out when we talk and breathe, according to their study, published in The Journal of Medical Virology.
The team of researchers measured how effective certain solutions were at killing coronavirus cells in a test flask. They tested a variety of peroxide sore-mouth cleansers and mouthwashes, and a 1% solution of baby shampoo and a neti pot saline rinse (the latter two of which are sometimes used for nasal irrigation). The mouthwashes and the baby shampoo treatment were both effective, while the peroxide cleanser and saline rinse were not.
The efficacious mouthwashes — which included Listerine Antiseptic, Orajel Antiseptic Rinse, and Crest Pro‐Health — appeared to kill more than 99.9% of the virus after 30 seconds or more of gargling and swishing. (The diluted baby shampoo was most effective, but in real life it's more difficult to use. You should consult a doctor before attempting it, in order to learn proper technique and dilution.)
The researchers conceived of the study back in March, hoping to find a way to add an extra layer of protection for folks. “Our goal was always to think about lowering the risk of spreading [viruses such as COVID-19],” Craig Meyers, PhD, a distinguished professor of microbiology and immunology, and obstetrics and gynecology at Penn State College of Medicine, tells Refinery29. “Yes, people should still wear a mask. But let’s say someone tests positive, and they live with people they can’t very well isolate themselves from. Gargling mouthwash would add another layer, and lower the amount of infectious virus they might be spewing out of their mouth.”
Before you run out to the pharmacy and buy Walgreens out of mouthwash, know that this research is in the very early stages. The team of scientists haven’t done clinical trials on humans yet, and they tested with a coronavirus associated with common colds, rather than the one that causes COVID-19. It could be promising as an added layer of protection, but experts told The New York Times that mouthwash is no silver bullet. The coronavirus the study looked into, 229E, and SARS-CoV-2 — the virus that causes COVID-19 — are in the same family and anatomically similar, but not totally interchangeable, Angela Rasmussen, PhD, a virologist at Columbia University, told The Times. However, Meyers points out that in a similar study published back in August, researchers at Ruhr-University Bochum in Germany found that actual SARS-COV-2 virus could be inactivated with some mouthwashes.
Meyers notes he’s itching to do a clinical trial, and says more research is needed to determine how the effective solutions would interact with the virus in the human mouth, and how often someone might need to use them in order to keep the virus mostly inactive to prevent the spread of droplets. There are also questions about what exact ingredients or combinations of ingredients in the solutions are killing the virus.
Procter and Gamble, the parent company of Crest Pro Health, did not respond to a request for comment from Refinery29 regarding the study and whether sales have gone up since the findings were released.
A spokesperson for Johnson & Johnson, the parent company of Listerine, said in a statement to Refinery29: "Listerine Antiseptic is an antimicrobial mouthwash that is clinically proven to kill germs that cause plaque, bad breath, and the early gum disease, gingivitis." They emphasized it's not intended to prevent or treat COVID-19 and should be used only as directed on the product label.
"To date, the available data is not sufficient to support a conclusion that the use of Listerine or mouthwashes could be helpful against coronavirus as further research is needed," the spokesperson said. "As a company firmly rooted in science, we will be active participants in the scientific exchange on this topic."
In the long run, this is certainly not a cure for COVID-19, but Meyers says it was never designed to be that way. “No, mouthwash won't cure COVID-19, but that’s never what we said it would do,” he says. “But this does have potential to stop spread.”
The takeaway: No matter what future research says about mouthwash, continue to wear a mask. Experts and health organizations have said time and time again that they work at preventing the spread of the potentially fatal virus. If you do start using mouthwash more often, consider it something you do in addition to everything you've already been doing — not a substitute.