Mouthwash is probably a part of your daily routine already, and you've no doubt been staring at that "fights 99.9 percent of germs!" packaging for so long, you forget you're even looking at it. With all of the hand washing and mask wearing we're doing, it's natural to wonder if that protective capability extends to the coronavirus as well. Hollywood seems to think so - see Camila Mendes and KJ Apa swishing mouthwash before kiss scenes on the set of Riverdale - so should the rest of us add this to our COVID-19 protection routine?
How Mouthwash Interacts With SARS-COV-2
The structure of a SARS-CoV-2 particle (the virus particle that causes COVID-19) is a big reason why mouthwash might be effective against it - so allow us to get into the science for a minute. A SARS-CoV-2 particle is surrounded by a fatty (or lipid) membrane. While this "envelope" may help the virus survive and infect other cells, it's also particularly vulnerable to soaps and detergents, which is why we've been told to wash our hands so much; the ingredients in the soap and detergent can break down that protective barrier.
What does that have to do with mouthwash? "Enveloped viruses like influenza, herpes simplex, and other coronaviruses are sensitive to common ingredients in mouthwash," explained Valerie O'Donnell, PhD, director of the division of infection and immunity and co-director of the Systems Immunity Research Institute at Cardiff University, in an interview with Healthline. In a study Dr. O'Donnell led in June, researchers also noted that the throat and salivary glands may be major sites of virus replication and transmission early on in COVID-19. Developing a way to safely target those areas could be a big breakthrough.
However, Dr. O'Donnell stressed that research on mouthwash's protection against other diseases was done via test tube experiments, "not from studies on viruses in the mouth, where their response may be different, and where little work has been done." And while research is coming to light about mouthwash and coronavirus, there's still a lot we don't know.
Can Mouthwash Protect Against COVID-19?
With those caveats, there is emerging evidence that mouthwash could reduce the viral load (aka the amount of coronavirus particles) and potentially lower the risk of coronavirus transmission over the short term, according to an August study out of Germany. In the study, researchers mixed different kinds of mouthwash with virus particles and a substance meant to mimic saliva, then shook each mixture for 30 seconds to simulate gargling. All of the mixtures, they found, had fewer virus particles afterward.
A more recent study from October also showed positive signs. Researchers from Penn State replicated the interaction of human coronaviruses (of which SARS-COV-2 is one) in nasal and oral cavities with several different products, including a 1-percent solution of baby shampoo, a neti pot, peroxide sore-mouth cleansers, and mouthwashes. They then measured the viral load left in the solution, finding that several products inactivated more than 99.9 percent of virus particles after 30 seconds. If the virus reacts similarly outside of lab settings, the mouthwashes and gargle products could help reduce spread, researchers said.
A third study from the UK found that mouthwashes containing both ethanol and either essential oils or a compound called ethyl lauroyl arginate (LAE) were most effective at eradicating viral particles after 30 seconds of exposure in a lab. Researchers listed Listerine Antiseptic as an example of a mouthwash containing essential oils and Listerine Advanced as one containing LAE. (On its website, Listerine maintains that its mouthwashes do not kill coronavirus particles.)
To clarify, "gargling with a mouthwash cannot inhibit the production of viruses in the cells," said researcher Toni Meister, part of the German study. What it could do is reduce the viral load in the short term, in the areas where the "greatest potential for infection comes from," aka the mouth and throat. This could be very helpful in certain situations, Meister added, such as at the dentist or during medical care for COVID-19 patients.
In other words, mouthwash isn't a treatment for COVID-19, but could potentially lower your risk for infection and transmission to others. So gargle away, but continue to practice other safety measures like socially distancing, wearing a mask, and washing your hands often.