Compound in some mouthwashes may suppress COVID-19, study finds

A chemical found in some mouthwashes may suppress COVID-19 infection by blocking the entry of the SARS-CoV-2 virus into the cells, a study has found.

Commercially available mouthwashes contain a number of antibiotic and antiviral components that act against microorganisms in the mouth, the researchers said.

One of these, cetylpyridinium chloride (CPC) has been shown to reduce the viral load of SARS-CoV-2 in the mouth, primarily by disrupting the lipid membrane surrounding the virus, they said.

While there are other chemicals with similar effects, CPC has the advantage of being tasteless and odourless, according to the researcher.

The team at Hokkaido University in Japan studied the effects of CPC in Japanese mouthwashes which typically contain a fraction of the chemical compared to previously tested mouthwashes.

They tested the effects of CPC on cell cultures that express trans-membrane protease serine 2 (TMPRSS2), an enzyme required by the SARS-CoV-2 for entering the cell.

The study, published in the journal Scientific Reports, found that, within 10 minutes of application, 30–50 microgrammes per millilitre (µg/mL) of CPC inhibited the infectivity and capability for cell entry of SARS-CoV-2.

Commercially available mouthwashes that contain CPC performed better than CPC alone, the researchers said.

The study also showed that saliva did not alter the effects of CPC.

The researchers then tested four variants of SARS-CoV-2 — the original, Alpha, Beta and Gamma — and showed that the effects of CPC were similar across all strains.

This study shows that low concentrations of CPC in commercial mouthwash suppress the infectivity of four variants of SARS-CoV-2.

The researchers have already begun assessing the impact of CPC-containing mouthwashes on viral loads in saliva of COVID-19 patients.

Future work will also focus on fully understanding the mechanism of the effect, as lower concentrations of CPC do not disrupt lipid membranes.