Study: Mouthwashes, Oral Rinses May Inactivate Human Coronaviruses

A new Penn State College of Medicine study has found that certain oral antiseptics and mouthwashes may have the ability to inactive human coronaviruses. The findings indicate that some of these products might be useful for reducing the viral load in the mouth after infection and may help reduce the spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2).

Physicians and scientists tested several oral and nasopharyngeal rinses in a laboratory setting for their ability to inactivate human coronaviruses that are similar in structure to SARS-CoV-2. The products evaluated include a 1% solution of baby shampoo, a neti pot, peroxide sore-mouth cleansers, and mouthwashes.

The researchers found that several of the nasal and oral rinses have a strong ability to neutralize human coronavirus, which suggests that these products may have the potential to reduce the amount of the virus spread by people who are coronavirus disease 2019 (COVID-19)-positive, according to the study authors.

Further, the researchers used a test to replicate the interaction of the virus in the nasal and oral cavities with the rinses and mouthwashes. The solutions were treated with 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.

The solutions interacted with the virus for 30 seconds, 1 minute, and 2 minutes, before diluting the solutions to prevent further inactivation. The outer envelopes of the human coronavirus in the tests and SARS-CoV-2 are genetically similar, which lead the researchers to hypothesize that a similar amount of SARS-CoV-2 may be inactivated upon exposure to the solution.

To measure how much the virus was inactivated, the researchers placed the diluted solutions in contact with cultured human cells. After counting how many cells remained alive after a few days of exposure to the viral solution, this number was used 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 results showed that the 1% baby shampoo solution, which is often used by head and neck doctors to rinse the sinuses, inactivated greater than 99.99% of human coronavirus after a 2-minute contact time, according to the study. Additionally, several of the mouthwash and gargle products also were effective at inactivating the infectious virus. Many inactivated greater than 99.99% of the virus after only 30 seconds of contact time and some inactivated 99.99% of the virus after 30 seconds.

Craig Meyers, lead author of the study and researcher at Penn State Cancer Institute, noted that the results with mouthwashes are promising and add to the findings of a prior 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, the researchers studied OTC products and nasal rinses that were not evaluated in the prior study.

Meyers said the next step to expand upon these results is to design and conduct clinical trials that evaluate whether products such as 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 health care workers are at a constant risk of exposure,” Meyers said in a press release. “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.”

Future studies may include a continued investigation of products that inactive human coronaviruses and what specific ingredients in the solutions tested inactivate the virus.

REFERENCE

Mouthwashes, oral rinses may inactivate human coronaviruses. PennState. https://news.psu.edu/story/635101/2020/10/19/research/mouthwashes-oral-rinses-may-inactivate-human-coronaviruses#:~:text=Penn%20State%20College%20of%20Medicine,when%20talking%2C%20sneezing%20or%20coughing.. Published October 20, 2020. Accessed October 20, 2020.