Could commercially-available mouthwash be used to help slow the spread of COVID-19? A group of scientists at the University of Cardiff have called for mouthwashes to be tested on SARS-CoV-2, the virus that causes COVID-19, after finding that some mouthwashes have anti-viral activity.

They suggest that mouthwash containing alcohol or other formulations might reduce the amount of virus in the throat and saliva of an infected person, which might reduce their symptoms and also make them less infective.

However, mouthwash has not been tested against SARS-CoV-2 yet, so we do not know whether this would help. Good quality trials would be needed before this could be recommended for preventing the spread of the virus. In the meantime, people should follow the instructions for use as on the bottle.

People should continue to follow the rules about social distancing and hand hygiene, rather than relying on the use of mouthwash for protection.

Where did the story come from?

Several media articles have reported on the Cardiff researchers’ call for testing mouthwashes on SARS-CoV-2. Suggestions that rinsing or gargling could help against the virus have been circulating for some time. In countries where rinsing with saline or mouthwash is part of the usual hygiene (such as Japan), it is a recommended preventive measure against respiratory disease.

What is the basis for the claim?

The researchers at Cardiff summarised studies about mouthwash and viruses that had already been published to see if there was any evidence that mouthwash might be helpful against SARS-CoV-2.

The researchers found that several ingredients of mouthwash, including alcohol, had been shown to damage lipid envelopes similar to those surrounding coronaviruses, although they have not been tested directly on SARS-CoV-2.

Mouthwashes have much lower concentrations of alcohol than those in hand sanitiser. Sanitiser is usually about 60% to 70% alcohol, while commercially-available mouthwashes range from about 14% to 27%. They may also contain essential oils such as menthol and eucalyptus oil. Another commonly-used chemical in mouthwash in the UK is chlorhexidine.

The researchers said there is evidence that commercially-available mouthwash formulations of alcohol plus essential oil could inactivate herpes virus and flu virus when used as a 30-second rinse. Chlorhexidine has only been tested against viruses in the laboratory, not in use by people. The researchers say a study showed it had only weak activity against a coronavirus and suggest it could be combined with alcohol.

The Cardiff researchers said scientists needed to find out whether rinsing with mouthwash would reduce the amount of virus in the mouth and throat, which mouthwash would be most effective, and what rinsing regime would be most effective to reduce the spread of the virus. The safety of gargling, as opposed to rinsing the mouth, with alcohol and chlorhexidine mouthwashes also needs further evaluation.

What do trusted sources say?

Gargling is not currently recommended to protect against COVID-19. Harvard TH Chan School of Public Health says: “There is no evidence that regularly gargling [saltwater or saline] has protected people from infection with the new coronavirus. While this may help soothe a sore throat, this practice will not prevent the virus from entering your lungs.”

Analysis by EIU Healthcare, supported by Reckitt Benckiser

 

Citation

  1. O’Donnell V et al. Potential role of oral rinses targeting the viral lipid envelope in SARS-CoV-2 infection. Function, zqaa002, https://doi.org/10.1093/function/zqaa002 (Accessed 28 May 2020)