It’s looking increasingly likely that mouthwash could be a potentially powerful tool in protecting against Covid-19.

A preprint study, which has not yet been peer-reviewed by other scientists, found certain widely-available mouthwashes eliminated the virus in test tube experiments.

The study, by Cardiff University researchers, created conditions that mimicked the back of the nose and throat. They then tested the ability of several high street mouthwashes to inactivate the virus which causes Covid-19.

Three mouthwashes were found to eliminate live virus in 30 seconds: Dentyl Dual Action, Dentyl Fresh Protect and Listerine Advanced.

Researchers told Sky News that Venture Life Group, which makes Dentyl, provided information to the study but did not fund it. The same company will fund the next stage of research.

The scientists said further studies are warranted to determine whether these formulations can actually inactivate the virus in humans, and whether this might impact transmission of the virus going forward. 

How does mouthwash work on Covid-19?

We know that detergents such as washing up liquid and soap can dismantle the fatty (lipid) membrane which holds the virus together.

Back in May, scientists suggested mouthwash could also be used to damage this membrane as a possible way to inactivate the virus in the throat.

Previous studies have shown agents commonly found in mouthwashes – such as low amounts of ethanol, povidone-iodine and cetylpyridinium – could disrupt the lipid membranes of enveloped viruses like SARS-CoV-2.

Dr Richard Stanton, lead author on the study and a reader in virology at Cardiff University, says: “This study adds to the emerging literature that several commonly available mouthwashes designed to fight gum disease can also inactivate the SARS-CoV-2 coronavirus – and other related coronaviruses – when tested in the laboratory under conditions that are designed to mimic the oral/nasal cavity in a test tube.”

He points out the study has yet to be scrutinised by other scientists, as is the usual process with academic research. 

Professor Jean-Yves Maillard, an expert in pharmaceutical microbiology at Cardiff University, noted that some points from the study may change once the results are peer-reviewed.

He said: “Overall, antimicrobial mouthwash may help in decreasing viral load in the oropharynx but this should not been viewed as using mouthwash instead of face masks, but instead as a potential combined intervention: use of mouthwash and wearing face masks. The remaining question is how often one needs to use a mouthwash to really make an impact? This would need to be answered before any recommendations are made.”

So, what happens next?

The University Hospital of Wales will now conduct a 12-week clinical trial to see if mouthwash can reduce the viral load in patients’ saliva.

“It is notable that coronaviruses are far more amenable to disruption than many other viruses and bacteria due to the presence of a viral lipid envelope,” says Dr Stanton.

“In the human throat, the virus is being produced constantly, so if there is an effect it will be important to see how long it lasts for and whether this could help reduce transmission, for example in dental investigations, mouth/throat examinations by GPs, or short-term contacts with vulnerable patients or other individuals.”

In the meantime, he urges people to continue to follow the preventive measures issued by the UK government, including washing hands frequently and maintaining social distance. “We would encourage people to always use mouthwash safely and as per the manufacturer’s guidelines,” he added.