Does Mouthwash Kill the Coronavirus?

"We're not trying to say it's a cure,” says Craig Meyers, professor of microbiology and immunology at Penn State College of Medicine and coauthor of the study. “We're not telling people to go out, now you can take off your mask and just gargle all the time. Keep wearing your mask, keep social distancing; do those things that we know work. This is just another layer on top of it."

Clinical trials could answer critical questions

The concept of using antiseptics to get rid of germs lurking in the nose and mouth is not new. “It's been very extensively studied” and implemented by doctors and dentists before procedures and exams, explains Henry T. Hoffman, M.D., professor of otolaryngology at University of Iowa Carver College of Medicine, who was not involved in the studies mentioned. But with the coronavirus pandemic showing no signs of slowing down, both Hoffman and Meyers say the use of antiseptic rinses may prove beneficial outside of the health care setting, especially in situations where close contact is unavoidable, such as in long-term care facilities and on airplanes.

The federal government's registry of clinical trials shows there's interest in this notion, as well. Several planned, active and recently completed trials are testing the effectiveness of mouth and nasal rinses against SARS-CoV-2 in human participants, which Meyers says is the next step. (Critics of the available research on oral and nasal rinses and the coronavirus point out that the studies were conducted in the lab and not in the mouth, which could alter the outcome.)

In addition to pinning down how well these rinses work at reducing the amount of virus in the mouths of people with COVID-19, determining the ingredients responsible for stripping the virus and the amount of time the rinsed area remains free of it will also be important. Meyers points out that certain oral and nasal rinses may have the ability to kill germs in the mouth and nose, but they won't erase “the virus that's inside your cells or down in your lungs.” The virus residing in other areas of the body is “going to repopulate,” Hoffman adds, so knowing how long the mouth and nose can potentially stay free of virus before more is produced is key.

"We need to really understand how often we need [to use the rinses] and get some more data on how it should be used within the community,” Meyers says. “Do we know it's going to stop the spread or lessen the spread? We can't say that unequivocally, but the data we have so far really suggests that's a possibility.”

Mouthwash doesn't replace masks

One of the benefits of the theory: For many people, adding an antiseptic rinse to their routines isn't a big ask. “This is something anybody can go to the store, buy and use it the way it's meant to be used and maybe lessen the spread” while we wait for a vaccine, Meyers points out.

That said, there are some risks associated with misusing rinses. One potential downside: Frequent use could change the microbiome in the mouth and nose, which includes the good germs, Hoffman points out. Alcohol-based mouthwashes can also lead to irritation, and iodine-based rinses can interfere with the function of the thyroid. Similar to other chemicals that kill the coronavirus, misusing the rinses by swallowing them or inhaling them can also cause harm.

Listerine's website maintains that while the antiseptic has been proven to kill 99.9 percent of germs that cause bad breath, plaque and gingivitis, it is not intended to prevent or treat COVID-19. It also shouldn't be used as a hand sanitizer or surface disinfectant, the company says.

Hoffman's advice: If you're interested in adding an antiseptic rinse to your routine, consult a doctor or dentist for advice on what you should use and how you should use it.

Currently, the best protection against COVID-19 is a mix of frequent handwashing, avoiding close contact with others, cleaning and disinfecting high-touch surfaces, and wearing a mask in public settings, according to the Centers for Disease Control and Prevention (CDC).

"Compared to wearing a mask and social distancing and washing your hands, [using a nose or mouth rinse] is probably a relative drop in the bucket,” Hoffman says. “But it may be an important drop in the bucket.”