En español | A swirl of mouthwash may be good for more than minty-fresh breath. A few recent studies suggest that certain oral rinses have the potential to help reduce transmission of the new coronavirus, though more research is needed to determine just how big of a role they can play in slowing the spread of COVID-19.
Researchers out of Penn State College of Medicine tested several oral and nasal rinses for their ability to inactivate a human coronavirus — not the one that causes COVID-19, but its cold-causing cousin that is similar in structure. All coronaviruses are surrounded by a membrane that is susceptible to soaps, alcohol and certain chemicals, and destroying this membrane is key to inactivating the virus.
What they found is that a few common over-the-counter products — including Crest Pro-Health, Listerine Ultra, Listerine Antiseptic and similar store-brand antiseptics — killed over 99.9 percent of the human coronavirus after 30 seconds of exposure in a laboratory setting. A 1 percent solution of baby shampoo, which is often recommended by doctors to rinse the sinuses, also mostly inactivated the virus after two minutes. The study was published in the Journal of Medical Virology.
What's more, researchers in Germany found that a few commercially available oral rinses, including an iso-Betadine mouthwash and Listerine Cool Mint, “significantly reduced viral infectivity” of SARS-CoV-2 — the coronavirus responsible for the current pandemic — “to undetectable levels” after an exposure time of 30 seconds in a laboratory setting. The study appears in The Journal of Infectious Diseases.
The authors of both peer-reviewed reports suggest that while these easily accessible products won't treat COVID-19 or protect you from getting infected, they could help reduce the amount of virus a person with COVID-19 has in the mouth and nose, which are major points of entry and transmission for the coronavirus. And, along with other preventive efforts such as face masks and hand hygiene, they could serve as one more tool to help slow the spread of SARS-CoV-2, which has so far infected nearly 45 million people worldwide.
"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.)
Protect yourself from COVID-19
- Wash your hands often with soap and water for at least 20 seconds, especially after you have been in a public place.
- If you don't have access to soap and water, use a hand sanitizer that contains at least 60 percent alcohol.
- Avoid close contact with others: Keep a distance of at least 6 feet from people who don't live in your household.
- Cover your mouth and nose with a mask when you are around other people.
- Cover your coughs and sneezes (and then wash your hands).
- Clean and disinfect frequently touched surfaces daily.
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.”