Fact Check-Mouthwash might reduce SARS-CoV-2 viral load in the mouth for a short time, but it is not a COVID-19 cure

Updated to include quotes from Dr Daniel Fine

U.S. Republican Senator Ron Johnson has claimed that mouthwash is proven to kill the SARS-CoV-2 virus.

While one study found some mouthwashes may reduce viral load in the mouth, they do not kill the virus in the nose or lungs, nor is it a cure for the disease.

In an audio recording shared on social media (here), which was taken during a telephone town hall with Wisconsin constituents, Johnson remarked: “By the way, standard gargle mouthwash has been proven to kill the coronavirus. If you get it, you may reduce viral replication. Why not try all these things?”

Johnson later pointed on Twitter to a study that looked into the effect an antiviral mouthwash known as CDCM could have on an infected individual’s SARS-CoV-2 salivary viral load (here).

The study (here), which consisted of 154 volunteers, found that CDCM mouthwash reduced SARS-CoV-2 salivary viral load by 71%, four hours after intake, for adults who had asymptomatic to mild COVID-19. It concluded that the mouthwash could as such act as a barrier measure against the spread of COVID-19.

But experts have warned that any possible effect on COVID-19 would likely be limited.

Dr Richard Stanton, a virologist at Cardiff University who has studied the impact of mouthwash on COVID-19 (here), told Reuters that while mouthwash can kill SARS-CoV-2 in the lab, it also depends heavily on which mouthwash is used.

“Some are very effective, others are not effective at all,” he said.

Furthermore, mouthwash will not cure a person of COVID-19.

“Mouthwash is only going to kill the virus in the mouth. It’s not going to have any impact on virus in the nose or lungs,” Stanton explained in an email. “This means it is unlikely to have an impact on disease.”

It is also unlikely to have much impact on transmission in the community.

Since the virus is always being replenished from the mouth, nose and lungs, Stanton said the mouthwash would only reduce live virus in the mouth for a short amount of time.

However, because many people may be unknowingly carrying the virus, he notes, mouthwash could have a role to play when a healthcare worker or dentist needs to do an investigation of the mouth or throat.

Even under these circumstances, Stanton maintains PPE is the most important factor to reduce risk.

“However, if a patient used a mouthwash before the investigation (as well as PPE), this would reduce the risk of accidental exposure even more,” he said.

Dr Daniel Fine, Chair of Oral Biology at Rutgers University, told Reuters that more research into the impact of mouthwash on COVID-19 was needed.

According to a study co-authored by Fine, two types of mouthwash can disrupt SARS-CoV-2 under laboratory conditions (here).

However, this research was not intended to suggest mouthrinsing against COVID-19 in a real-world scenario, as more in-depth study is required, he said.

“The comments by the Senator Johnson’s comments are misleading and serve as a way of distracting the public from tested/proven preventive and therapeutic methods,” Fine added.

Listerine (here), the top-selling mouthwash brand in the United States, has warned its product is “not intended to prevent or treat COVID-19 and should be used only as directed on the product label.”

“Although there are recent lab-based reports of some mouthwashes having activity against enveloped viruses, including coronavirus, the available data is insufficient,” its guidelines add.


Missing context. While one study found antiviral mouthwash may reduce the viral load of SARS-CoV-2 in the mouth, it does not reduce overall viral load, and it is not a cure for the disease.

This article was produced by the Reuters Fact Check team. Read more about our fact-checking work   here.