As some scientists work on potential COVID-19 vaccines, others are looking to existing products to slow the rate of coronavirus infection, including mouthwashes and oral rinses.

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Alcohol-based hand sanitizers and wipes play an important part in reducing infection rates. However, other products might also have a role to play. Scientists at the Penn State College of Medicine in Hershey, PA, are looking at oral rinses and mouthwashes.

In a recent study, which appears in the Journal of Medical Virology, researchers determined that several oral and nasal solutions might lower the risk of viral transmission when used by those with a coronavirus infection.

Craig Meyers, professor of microbiology and immunology and obstetrics and gynecology, led the study. “While we wait for a vaccine to be developed, methods to reduce transmission are needed,” Meyers says. “The products we tested are readily available and often already part of people’s daily routines.”

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To investigate, Meyers and his team used a human respiratory virus called HCoV-229E, which is in the same virus family as SARS-CoV-2. In a laboratory, they introduced various products to the virus to assess whether they could successfully reduce viral activity.

The selected nasal products included a diluted Johnson’s Baby Shampoo nasal rinse and a CVS Health Neti Pot. The mouthwash gargling products tested were CVS Health Peroxide Sore Mouth Cleanser, 1.5% Hydrogen Peroxide solution (Cumberland Swan Inc.), Orajel Antiseptic Rinse (Church & Dwight Co. Inc.), Betadine 5% (Alcon Laboratories Inc.), Crest Pro-Health (Procter & Gamble), Listerine Antiseptic (Johnson & Johnson Consumer Inc.), Listerine Ultra (Johnson & Johnson Consumer Inc.), Equate (Walmart), and Antiseptic Mouthwash (CVS Health).

Researchers exposed the human coronaviruses to each solution in three separate tests lasting 30 seconds, 1 minute, and up to 2 minutes. While most of the selected products showed some level of impact, the neti pot had no measurable effect across any of the tests.

The Johnson’s Baby Shampoo nasal rinse solution killed 99% of the coronaviruses within 1 minute and 99.9% within 2 minutes. Crest Pro-Health reduced the coronaviruses from 99.9% to greater than 99.99%.

The most impactful product was Listerine Antiseptic, which managed to reduce the virus by greater than 99.99% after 2 minutes. Overall, the Listerine and Listerine-like mouthwashes produced the best results.

The findings further validated similar results published in the Journal of Infectious Diseases in July 2020. In this earlier study, the authors determined that routine oral rinsing by those with a coronavirus infection might reduce the viral load in their mouths, throat, and nose. This could potentially reduce the amount they could transmit to others with a cough or sneeze.

Additionally, the research team found it interesting that the three products with hydrogen peroxide as the main ingredient inactivated the virus at a rate between 90 and 99%. This result supports previous research that also found hydrogen peroxide solutions to be effective against SARS-CoV-2.

Taken together, there is enough research available to strongly suggest that these products could help reduce the transmission of SARS-CoV-2 between someone with an infection and someone without an infection.

Meyers explains: “People who test positive for COVID-19 and return home to quarantine may possibly transmit the virus to those they live with. Certain professions, including dentists and other healthcare workers, are at a constant risk of exposure.”

Use of these over-the-counter solutions, when combined with other preventive methods, could offer an even greater level of protection among the general public.

That said, there are some important aspects of the study to consider that might impact the overall accuracy of the outcome expected against SARS-CoV-2.

For instance, as the authors explain, “We did not use SARS-CoV-2 in this study as the virus, as it was more expensive, less available, and would have required biosafety level-3 laboratory conditions.”

Also, the tests were conducted in laboratory conditions rather than in human participants. As the authors explain, “[T]his does not represent the true nature of the nasopharyngeal endothelial ecosystem.”

Meyers and his team strongly advocate for future trials. With more accurate testing, it might be possible to eventually create a comprehensive prevention strategy that is easy, widely available, and affordable.

It is also important to note that, even if further research confirms the antiviral benefits of mouthwash use, these products cannot replace face coverings, social distancing, and other methods. They will be an additional tool.

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