Some mouthwashes may be able to kill the novel coronavirus in 30 seconds or less, according to a new study from researchers at Cardiff University in Wales. Their work was recently published online this month, though it has not yet been published in a peer-reviewed journal, and the research was done in lab settings only. If verified with more studies, the results could give healthcare workers a new, promising tool to slow the spread of the pandemic. However, even if household mouthwash does kill off the virus in your saliva temporarily, that doesn’t mean your daily gargle is enough to prevent you from catching—or spreading—COVID-19.
The researchers studied two chemicals commonly found in mouthwash, cetylpyridinium chloride and ethanol/ethyl lauroyl arginate, to see if they could kill SARS-CoV-2, the virus that causes COVID-19, in a controlled lab setting. The results showed that within 30 seconds after exposure, the levels of live virus decreased to below the threshold for transmission. This was all done in a lab setting though, and the authors of the study note that additional research is required to see if these results can be replicated in human subjects. Further, the study’s conclusions don’t suggest that mouthwash would be able to prevent all COVID-19 transmission.
“Respiratory droplets that get expelled are not just coming from saliva,” says Daniel Brian Nichols, an associate professor of biological sciences at Seton Hall University who studies virus-host interactions. “They’re also coming from mucus, so [mouthwash is] not going to kill all the virus.”
Not only can you expel the virus from your nose as well as your mouth, those aren’t the only places in your body that hold virus particles when you’re infected. SARS-CoV-2 particles latch onto body cells in your respiratory, cardiovascular, and gastrointestinal systems as well, and it doesn’t take a very long time after killing the virus in your saliva for the particles in the rest of your body to return to your mouth. “Within a couple of hours, it starts to accumulate again inside the saliva,” says Nichols.
That’s why it’s important that, even if you’re constantly gargling mouthwash, you keep wearing a mask when around other people, practice proper social distancing when around others, and washing your hands frequently. These are effective ways that we know slow the spread of the novel coronavirus.
So mouthwash probably won’t stop you from spreading COVID-19—at least not for very long. However, it could potentially help protect healthcare workers from unnecessary exposure to the virus in the short term.
“Inside of a clinical setting, if you have patients who are COVID-positive, you could reduce their viral loads for the doctors and nurses who are examining them by having them gargle some mouthwash,” says Nichols.
Using mouthwash to lower the viral load in your saliva should also not be done before you go get a test, Nichols warns: “You run the risk of a lot of these tests coming back as false negatives.”
Since the mouthwash kills most of the virus in your mouth, those levels will remain lower than usual for a short time, and may put the levels below the threshold that a PCR test will detect. So while it’s still important to use mouthwash to keep up with your dental hygiene, that shouldn’t be your first line of defense against transmitting COVID-19.