Sorry, Mouthwash Isn’t a Coronavirus Cure

Mouthwash is designed to kill germs in your mouth. It is, I’d have to say, pretty good at its job. And yet: we do not seriously trust mouthwash to prevent the transmission of common colds, strep infections, or any other mouth-germ-y illness. We shouldn’t get our hopes up it will be an effective way to avoid getting COVID-19 either.

There have been a few studies testing the effects of mouthwash on SARS-CoV-2 (the coronavirus that causes COVID-19) and they are interesting and potentially useful, especially for healthcare workers. For example, if using mouthwash before a dental visit temporarily reduces the amount of virus in your mouth, that might help reduce your dentist’s risk of getting sick.

And that’s really the level of protection that scientists are evaluating when they look at mouthwash and coronavirus. Unfortunately, the way some people are sharing the latest story, it seems like there is some hope that mouthwash is a new tool we can use to protect ourselves in our everyday lives. The study these breathless news articles are based on doesn’t support that conclusion, though — or at least not yet.

What’s the new study about?

The latest study on mouthwash, reported with headlines like “Common mouthwashes may help fight the coronavirus,” describes an experiment involving:

1. Human cells grown in the lab (not in an actual human being)
2. One of the other human coronaviruses.

That’s right, the virus being experimented on here is not the one that causes COVID-19, but a less harmful one called HCoV‐229e, one of the many viruses responsible for the common cold. What works against this virus probably also works against the one we’re worried about, so it was a fair choice for an experiment.

With this setup, the investigators tried a few different mouthwashes and drugstore products to see which ones inactivated most of the virus. Here’s what they said about the products that worked:

A 1% baby shampoo nasal rinse solution inactivated HCoV [the cold-causing coronaivirus] greater than 99.9% with a 2‐min contact time. Several over‐the‐counter mouthwash/gargle products including Listerine and Listerine‐like products were highly effective at inactivating infectious virus with greater than 99.9% even with a 30‐s contact time. In the current manuscript we have demonstrated that several commonly available healthcare products have significant virucidal properties with respect to HCoV.

(Not mentioned above because it didn’t pass the tests: a nasal rinse recipe included with a CVS neti pot, which involved salt and baking soda.)

This study is not the first to test the idea that mouthwash might help prevent transmission of COVID-19. A review published earlier this year breaks down the evidence that mouthwash should be able to help. Briefly: SARS-CoV-2 is an enveloped virus; ingredients in mouthwash can disrupt this type of envelope; less virus in your mouth probably means a lower chance of transmission. To be clear, if you’re infected, using mouthwash would result in a temporary reduction in the amount of infectious virus in your mouth. It wouldn’t make you any less sick.

This all makes sense, but nobody has tested this idea in anything approaching a real-world setting. The authors of the review laid out several of the questions that need to be addressed by future research, and they told SELF that clinical trials are underway.

What does this mean for me?

So far, not much. The most likely way this will affect your life is that someday your dentist or doctor may ask you to use mouthwash before or at the beginning of a visit.

This research does not mean that mouthwash is a substitute for wearing a mask, or that science has conquered the coronavirus. If you are infected, the virus is still reproducing in your cells and doing its best to escape and infect another host, whether you use mouthwash or not.

If mouthwash is already a thing you use and you feel like doing an extra swish or two, there’s a possibility that doing so will reduce your chances of transmitting the virus. But nobody has tested this specifically. If you’re thinking “well, it can’t hurt,” it’s also worth noting that mouthwash chemicals can sometimes be harsh and irritating, especially with frequent use. The best thing to do right now is to smile because you can see that researchers are working on this important question. Then continue wearing your mask and distancing as usual.