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Can Mouthwash Combat COVID-19? It Depends on Who You Ask

Woman Holding Mouthwash Thinking

In October, a group of researchers from the Ruhr-Universität Bochum in Germany received a lot of attention for their research project exploring the question, “Could mouthwashes reduce the risk of Coronavirus transmission?” While some touted the researchers’ discoveries as hopeful, others have been quick to point out some important shortcomings in the team’s findings.

The Big Idea: Fighting the Virus Where It Lives

The team of virologists conducting the study (published in the Journal of Infectious Diseases) based the experiment on two generally accepted assumptions: that COVID-19 is most likely spread by respiratory aerosols (droplets that are shared by sneezing, coughing, or talking) and that significant amounts of the virus (or viral loads) can be found in the mouths and throats of many COVID-19 patients. They then set out to see what effect, if any, certain mouthwashes would have on the virus, to determine if combatting the virus at its point of concentration might help to reduce its spread.

The Question Is: Which COVID Virus?

One of the biggest objections put forth by the study’s detractors is this: the virus used in the experiment was not THE COVID virus (SARS-CoV-2), but a very similar virus from the same family, HCoV‐229e (229E). Dr Angela Rasmussen, a virologist at Columbia University, is quoted in a New York Times article as noting that while 229E is a pretty good stand-in for SARS-CoV-2, “the two viruses shouldn’t be thought of as interchangeable.” The truth is, SARS-CoV-2 can only be studied in high-security labs by those who have undergone rigorous training — two necessities that neither this lab nor these researchers had.

The Experiment

The researchers chose eight different mouthwashes, with different active ingredients — including hydrogen peroxide, essential oils and others — to test. They mixed each mouthwash with virus (HCoV‐229e ) particles and another substance that was intended to recreate the effect of saliva in the mouth. The mixture was then shaken for 30 seconds to simulate the effect of gargling. Finally, they added cell material (from human liver cells) that is known to be particularly receptive to the virus, and then measured the quantity of virus that remained in each of the mixtures.

They discovered that while all the mouthwashes tested did reduce the viral load initially, three of them were able to reduce the load to the point that after 30 seconds of exposure, no virus was detected at all.

But What About OUTSIDE the Laboratory?

The other major issue that many scientists have with this study is that it was limited to the lab, that no human clinical data was gathered. As many of these experts point out, the environment of the human mouth is far more complex than that of a petri dish —both structurally and chemically. There are any number of hidden surfaces that could be tucked away and just out of reach of a mouthwash solution, and the chemical makeup of the oral cavity isn’t limited to just saliva.  

What It Means to Dental Care

At worst, the results from this study could be called dangerously misleading. Dr. Rasmussen offers this assessment, “You can use mouthwash to reduce your chance of getting gingivitis. I don’t think it’s going to have a meaningful impact on your ability to transmit this virus.”

And while even those who support the study certainly fall short of recommending that individuals use mouthwash as a protection against catching COVID-19, they do suggest that there could be a real benefit to using mouthwash in the fight against COVID-19 in the right situation. Because most of these mouthwashes have proven to be effective against the similar virus —reducing the viral load and possibly the risk of transmission over the short term —employing the mouthwashes (for example, prior to dental treatments) could be at least somewhat effective in reducing the spread of the virus.

Investigating Further

Either way, most experts agree that greater research needs to be conducted —specifically testing the effects of mouthwash on COVID-19 viruses in actual patients. Of particular interest is learning more about exactly how long lasting the effects of the mouthwashes could be. Currently, there are similar studies underway at the University of California San Francisco, and the German team is in contact with the American researchers there.

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