Human coronaviruses ‘inactivated’ by mouthwash, oral rinses: study

A new study conducted by researchers at the Penn State College of Medicine has found that a common dental item can inactivate human coronaviruses: mouthwash and oral rinses. 

For the study, the results of which were published in the Journal of Medical Virology, researchers tested various oral and nasopharyngeal rinses — which included a 1% solution of baby shampoo, a neti pot, peroxide sore-mouth cleansers, and mouthwashes — to determine how well they inactivated human coronaviruses. 

“While we wait for a vaccine to be developed, methods to reduce transmission are needed,” Meyers said in a statement. “The products we tested are readily available and often already part of people’s daily routines.” (iStock)

The baby shampoo solution, “which is often used by head and neck doctors to rinse the sinuses,” the researchers noted in a news release regarding the findings, was particularly effective; the solution inactivated “greater than 99.9% of human coronavirus after a two-minute contact time,” they said. 

The mouthwash and oral rinses were also efficacious, they found: “Many inactivated greater than 99.9% of virus after only 30 seconds of contact time and some inactivated 99.99% of the virus after 30 seconds.”

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More specifically, researchers “used a test to replicate the interaction of the virus in the nasal and oral cavities with the rinses and mouthwashes,” as the nasal and oral cavities are thought to be main points of entry for human coronaviruses, including SARS-CoV-2, better known as COVID-19. Though the researchers didn’t specifically test SARS-CoV-2 in the study, the novel virus is genetically similar to the other human coronaviruses tested, leading the researchers to hypothesize that the results would be similar. 

A strain of human coronavirus was mixed with “baby shampoo solutions, various peroxide antiseptic rinses and various brands of mouthwash,” allowing the solutions to iterate with the virus for different amounts of time, including 30 seconds, one minute, and two minutes. The solutions were then diluted to “prevent further virus inactivation,” they wrote. 

“To measure how much virus was inactivated, the researchers placed the diluted solutions in contact with cultured human cells. They counted how many cells remained alive after a few days of exposure to the viral solution and used that number to calculate the amount of human coronavirus that was inactivated as a result of exposure to the mouthwash or oral rinse that was tested,” per the news release. 

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Lead study author Craig Meyers, a distinguished professor of microbiology and immunology and obstetrics and gynecology, said the results show that the amount of virus (viral load)  in an infected person’s mouth could be reduced by using these common over-the-counter products, ultimately helping to reduce the spread of the novel virus. 

“While we wait for a vaccine to be developed, methods to reduce transmission are needed,” Meyers said in a statement. “The products we tested are readily available and often already part of people’s daily routines.”

The team’s findings bolster past research that also looked at how oral rinses and mouthwashes may be able to reduce the viral load of human coronaviruses. For instance, a study published in the scientific journal Function in May also concluded that mouthwash could play a role in preventing the transmission of the novel coronavirus. 

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Additionally, a more recent study published in The Journal of Infectious Diseases came to a similar conclusion. Meyers said that his findings add to this research, noting that his team evaluated the salutations at longer contact times in addition to studying “over-the-counter products and nasal rinses that were not evaluated in the other study.”

“People who test positive for COVID-19 and return home to quarantine may possibly transmit the virus to those they live with,” said Meyers. “Certain professions including dentists and other health care workers are at a constant risk of exposure. Clinical trials are needed to determine if these products can reduce the amount of virus COVID-positive patients or those with high-risk occupations may spread while talking, coughing or sneezing. Even if the use of these solutions could reduce transmission by 50%, it would have a major impact.”