The Effect Mouthwash Has on COVID-19 Requires Context

There's a growing list of studies that implicate the use of mouthwash can reduce the SARS-CoV-2 viral load, but context and common sense are imperative when interpreting the data.

By Genni Burkhart

According to a recent study published in The Journal of the American Dental Association, researchers at Ohio State University found that mouthwashes can reduce the SARS-CoV-2 viral load in saliva.

In March of last year, Researchers at Rutgers School of Dental Medicine also found evidence that "two types of mouthwash" can disrupt and prevent the COVID-19 virus from replicating in human cells under laboratory conditions. This study was published in the journal Pathogens and found the brand Listerine®, as well as the prescription mouthwash Chlorhexidine®, were able to disrupt the virus within seconds in laboratory conditions that mimic consumer use.

However, a dental-professional-focused website run by Listerine®, (the brand cited in the Rutgers study) states on their website (in bold) that their mouthwash, "is not intended to prevent or treat COVID-19 and should be used only as directed on the product label."

We'll look further at the tug-of-war over the efficacy of mouthwash on the SARS-CoV-2 virus and the implications of all this research.

There's a Lot of Studies on Mouthwash

The growing list of studies that implicate mouthwash (in many studies, Listerine®) regarding coronaviruses includes, but is not limited to:

  • In Vitro SARS-CoV-2 Clinical Isolates Data (Meister et al.; Ruhr University Bochum)
  • In Vitro Human Coronavirus 229e Data (Meyers et al.; Penn State College of Medicine)
  • The Virucidal Efficacy of Oral Rinse Components Against SARS-CoV-2 In Vitro (Statkute et al.; Cardiff University)
  • Differential effects of antiseptic mouth rinses on SARS-CoV-2 (Xu et al.; Rutgers University)
  • Effective in-vitro inactivation of SARS-CoV-2 by commercially available mouthwashes (Davies et al.; National Health Service (NHS), Public Health England)
  • Johnson & Johnson® Consumer Health sponsored a study with BioScience Laboratories to test Listerine® mouthwash in a U.S. laboratory.

This is just a sample in a sea of countless studies involving mouthwash. Listerine® goes on to list all of the current and pending studies, clearly stating that "Additional clinical research is needed to understand whether rinsing and/or gargling with LISTERINE® mouthwashes or other mouthwashes have potential to reduce the viral load in the oral cavity and oropharynx, and/or reduce the transmission of the virus."

Mouthwash in the Middle

Mouthwash has inevitably found its way into the coronavirus treatment quagmire, much like veterinary medications and cleaning supplies. But how did mouthwash end up here, and how does it get out?

For this, we look to Craig Meyers, a professor of microbiology and immunology at Pennsylvania State University and contributor at FactCheck.org ®, a nonpartisan, nonprofit organization that fact checks public policy issues.

Meyers states that while mouthwashes have shown clinical promise, they're laboratory-based. These mouthwashes might have been able to show an ability to inactivate the virus in vitro, but he cautions much of this research is done in a lab setting, outside the human body. He goes on to explain that in vitro studies are “pretty clear,” but that there's “no conclusive human studies that say yes or no." He goes on to tell interviewers that “you can do a lot of things” in vitro that “you can’t do in vivo.”

In other words, take the results from all of these mouthwash studies in context.

Meyers is also part of a team at Penn State conducting a randomized, controlled clinical trial on whether or not using mouthwash and/or a nasal wash can effectively reduce the viral load of SARS-CoV-2 in the mouth and nose of humans. This contactless trial includes approximately 200 participants who've been diagnosed with SARS-CoV-2 infection within the prior five days and are asymptomatic or only have mild ones. The purpose of this study is to test the potential of nasal pharyngeal and oral pharyngeal wash to reduce transmission of SARS-CoV-2.

It Comes Down to Common Sense

“If we can lower the amount of virus you have,” states Meyers at FactCheck.org, the likelihood of transmission is also reduced. If this new study can show a significant reduction in the amount of virus–which Meyers claims preliminary data seems "extremely promising," it doesn't also thereby prove there's a complete loss of transmission. Meyers goes on to say much of this is "common sense,” and they're hopeful to see a 50% reduction in transmission.

When it comes to solving this mouthwash quagmire, deciphering research from in vitro vs. in vivo is particularly important, and using common sense when interpreting the outcomes of these studies is paramount.

If research data does show a meaningful reduction in transmission from the use of oral pharyngeal washes, that's not the same thing as curing the COVID-19 virus, or providing a complete loss of transmission; to say that is misleading.

Evidence from current scientific data on mouthwash hasn't shown it to "cure" anything thus far, except perhaps, bad breath.

 

Author: With over 12 years as a published journalist, editor, and writer Genni’s career has spanned across technology, politics, healthcare, law, business finance, and the media. She resides on the idyllic western shores of the Puget Sound where she works as the Editor in Chief at DOCS Education out of Seattle, WA.

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