Study: Mouthwash may ‘inactivate’ human coronaviruses

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Results indicate some products might be useful for reducing amount of virus in the mouth after infection

Some oral antiseptics and mouthwashes might be able to inactivate human coronaviruses, making them possibly useful for reducing the amount of virus in the mouth after infection. This might help to reduce the spread of SARS-CoV-2, the coronavirus that causes COVID-19.

A group of physicians and scientists at the Penn State College of Medicine tested a 1% solution of several oral and nasopharyngeal rinses — including baby shampoo, a neti pot, peroxide sore-mouth cleansers and mouthwashes — in a laboratory setting for their ability to inactivate human coronaviruses, which are similar in structure to SARS-CoV-2.

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The researchers determined several of the nasal and oral rinses had a strong ability to neutralize human coronavirus, which suggests they might be able to reduce the amount of virus spread by people who are COVID-19 positive.

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

Recent studies have shown nasal and oral cavities to be key entry and transmission points for the coronavirus, so the researchers replicated the interaction of the virus in the nasal and oral cavities with the rinses and mouthwashes.

Meyers' team treated solutions containing a strain of human coronavirus — a readily available and genetically similar alternative for SARS-CoV-2 — with the baby shampoo solutions, various peroxide antiseptic rinses and various brands of mouthwash.

They allowed the solutions to interact with the virus for 30 seconds, one minute and two minutes, before diluting the solutions to prevent further virus inactivation. The outer envelopes of the human coronavirus tested and SARS-CoV-2 are genetically similar, the press release stated, so the research team hypothesizes that a similar amount of SARS-CoV-2 may be inactivated upon exposure to the solution.

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.

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The 1% baby shampoo solution, often used by head and neck doctors to rinse the sinuses, inactivated more than 99.9% of human coronavirus after two minutes of contact. Several of the mouthwash and gargle products also were effective. Many inactivated more than 99.9% of the virus after only 30 seconds of contact, and some inactivated 99.99% of the virus after 30 seconds.

Meyers said the next step is to design and conduct clinical trials to evaluate whether products like mouthwashes can effectively reduce viral load in COVID-19 positive patients.

“People who test positive for COVID-19 and return home to quarantine may possibly transmit the virus to those they live with,” said Meyers, a researcher at Penn State Cancer Institute and leader of the research team. “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.”

The study was published in the Journal of Medical Virology.

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