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Infectious Diseases

Updated 20 August 2020

Coronavirus transmission: Scientists ran lab experiments on mouthwash - this is what they found

This hygiene habit could do more than simply freshen your breath, and could help reduce the risk of spreading the virus, say researchers - but further studies are needed.

  • High viral loads can be detected in the oral cavity and throat of some Covid-19 patients
  • Researchers of a recent study state that mouthwash may reduce the levels of SARS-CoV-2
  • They are calling for further investigation into its effectiveness in fighting the virus

If an antibacterial mouthwash hasn’t become your best friend for oral care just yet, this might change your mind: according to the latest research, it could reduce the risk of SARS-CoV-2 (the virus that causes Covid-19) transmission.

The researchers, from Ruhr University Bochum in Germany, together with colleagues from five other German universities, found that SARS-CoV-2 can be inactivated using certain commercially available mouthwashes.

Their results were published in the Journal of Infectious Diseases, and a review of the laboratory results in clinical trials is pending.

Similar study done earlier this year

In May this year, the World Health Organization (WHO) said that there is “no evidence” that mouthwash can protect one against the new coronavirus. This was after a report was released, suggesting that the oral hygiene product could damage the virus and prevent infection.

Researchers say mouthwash chemicals chlorhexidine, cetylpyridinium, hydrogen peroxide, and povidone-iodine have the potential to prevent infections. Since high viral loads can be detected in the oral cavity and throat of some Covid-19 patients, gargling with a mouthwash that is effective against SARS-CoV-2 could help to reduce the viral load, and possibly the risk of virus transmission in the short term

Lead author of an earlier study this year, Professor Valerie O'Donnell, co-director of Cardiff University’s Systems Immunity Research Institute said:

“In test-tube experiments and limited clinical studies, some mouthwashes contain enough of known virucidal ingredients to effectively target lipids in similar enveloped viruses.

“What we don’t know yet is whether existing mouthwashes are active against the lipid membrane of SARS-CoV-2.”

O’Donnell and colleagues, therefore, called for further research to determine the potential of mouthwashes for use against the virus, and specifically look into whether mouthwash can destroy the “envelope” of the virus, which stops it from replicating. 

Current study: eight mouthwashes 

In the latest German study, the research team tested eight mouthwashes containing different ingredients that are available in pharmacies in Germany. 

They then mixed each mouthwash with virus particles and an interfering substance, which was intended to recreate the effect of saliva in the mouth. Following this, the effect of gargling was simulated by shaking the mixture for 30 seconds.

The next step involved using Vero E6 cells to determine the virus load. Vero cells are a lineage of cells used in cell cultures (the process by which cells are grown under controlled conditions), and Vero E6 cells are particularly receptive to Sars-CoV-2.

Clinical trials should follow

All of the tested preparations were found to reduce the initial virus load, and three mouthwashes reduced it to the point that no virus was detected after an exposure time of 30 seconds.

However, these effects have yet to be confirmed in clinical studies. The authors are therefore calling on further investigation. At the moment, similar studies are already underway in San Francisco, and the Bochum team is in contact with the US researchers.

Mouthwashes cannot treat Covid-19

The researchers also brought up an important point, which is that mouthwashes are not suitable for treating Covid-19 infections. 

"Gargling with mouthwash cannot inhibit the production of viruses in the cells," said study co-author Toni Meister in the university’s news release, adding: "But [it] could reduce the viral load in the short term where the greatest potential for infection comes from, namely in the oral cavity and throat – and this could be useful in certain situations, such as at the dentist or during the medical care of Covid-19 patients."