Some oral antiseptics and mouthwashes may be able to inactivate human coronaviruses, according to researchers at the Penn State College of Medicine who say that certain products might be useful for reducing the viral load in the mouth after infection and for reducing the spread of SARS-CoV-2.
The 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 evaluated products included a 1% solution of baby shampoo, a neti pot, peroxide sore-mouth cleansers, and mouthwashes.
Several of the nasal and oral rinses had a strong ability to neutralize human coronavirus, the researchers said, which suggests that these products may have the potential 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,” said Craig Meyers, MS, PhD, distinguished professor of microbiology and immunology and obstetrics and gynecology and leader of the study. “The products we tested are readily available and often already part of people’s daily routines.”
The researchers replicated 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.
The researchers treated solutions containing a strain of human coronavirus that 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 interaction.
According to Meyers, the outer envelopes of the human coronavirus tested and SARS-CoV-2 are genetically similar, so the researchers hypothesize 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 that was tested.
The 1% baby shampoo solutions, which head and neck doctors often use to rinse the sinuses, inactivated more than 99.9% of human coronavirus after two minutes. Several of the mouthwash and gargle products also were effective at inactivating the infectious virus. 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.
According to Meyers, the results with mouthwashes are promising 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 weren’t evaluated in the other study.
Meyers said 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. Certain professions including dentists and other healthcare workers are at a constant risk of exposure,” said Meyers, who also is a researcher at Penn State Cancer Institute.
“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,” Meyers said.
Future studies may include a continued investigation of products that inactivate human coronaviruses and what specific ingredients in the solutions tested inactivate the virus.
The study, “Lowering the Transmission and Spread of Human Coronavirus,” was published by the Journal of Medical Virology.