Mouthwashes and oral rinses may inactivate coronaviruses

Certain oral antiseptics and mouthwashes may have the ability to inactivate human coronaviruses, according to a new study by researchers at the Penn State College of Medicine and published in the Journal of Medical Virology.

The results indicate that some of these products might be useful for reducing the viral load, or amount of virus, in the mouth after infection and may help to reduce the spread of SARS-CoV-2, the virus that causes the novel coronavirus (COVID-19).

For the study, researchers tested several oral and nasopharyngeal rinses in a laboratory setting for their ability to inactivate human coronaviruses, which are similar in structure to SARS-CoV-2. The products evaluated include a 1 percent solution of baby shampoo, peroxide sore-mouth cleansers, and mouthwashes.

The tea used a test to replicate the interaction of the virus in the nasal and oral cavities with the rinses and mouthwashes. Nasal and oral cavities are major points of entry and transmission for human coronaviruses. They treated solutions containing a strain of human coronavirus, which served as 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.

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.

The researchers found that several of the nasal and oral rinses had a strong ability to neutralize human coronavirus, which suggests that these products may have the potential to reduce the amount of virus spread by people who are COVID-19-positive.

The results with mouthwashes are promising, the researchers said, and add to the findings of a study showing that certain types of oral rinses could inactivate SARS-CoV-2 in similar experimental conditions. In addition to evaluating the solutions at longer contact times, they studied over-the-counter products and nasal rinses that were not evaluated in the other study. The next step to expand upon these results is to design and conduct clinical trials that 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 Craig Meyers, MS, PhD, lead author of the study and a researcher at Penn State Cancer Institute, in a statement. "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."

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