Some health officials, however, caution that the evidence is preliminary, that mouthwash is no miracle cure, and that the infection can live on in a person despite gargling. In lab tests conducted at Penn State, scientists found that common mouthwash and gargle products like Listerine inactivated 99 percent of a strain of coronavirus genetically similar to the one that causes COVID-19 in just 30 seconds. “At one or two minutes, we couldn’t detect any infectious virus left using Listerine,” says lead study author Craig Meyers, PhD, a professor of microbiology and immunology and obstetrics and gynecology at Penn State College of Medicine in Hershey, Pennsylvania. A 1 percent solution of baby shampoo was also found to be highly effective in wiping out almost all the virus. Head and neck doctors often use such a treatment to rinse patient sinuses. On the other hand, the researchers found hydrogen peroxide rinses and neti pot rinses did very little to inactivate the virus. RELATED: From Nose to Toes, the List of COVID-19 Symptoms Keeps Growing
Human Trials Will Be the Real Test
Lab studies like the Penn State investigation, which was reported in September in the Journal of Medical Virology, have certain limitations when trying to apply their findings to people. “It’s important to realize that there is a difference between research conducted in a controlled laboratory setting and the dynamic microbial environment that exists inside your mouth,” says Robert Glatter, MD, a physician in the department of emergency medicine at Lenox Hill Hospital in New York City. “The two cannot be adequately compared due to the potential for so many other chemical influences and confounding factors which cannot be adequately measured and studied.” For Dr. Meyers and his team, the hope is that other trials involving human subjects will support their laboratory findings. “If we can test this in people, we can get the actual data that may show that if people do this, they can actually lower their viral load, which would mean that it has the potential to lower the virus’s ability to spread,” said Meyers. He notes that the University of California in San Francisco is planning to launch human trials assessing the effect of mouthwash and oral rinses on COVID-19 patients, and Vanderbilt University in Nashville is already conducting a clinical trial to determine whether nasal saline irrigations can reduce viral shedding and symptoms in patients with COVID-19. A goal will not only be to see if such rinses kill the virus in the mouth and nasal passages, but to assess how long-lasting the treatments may be. RELATED: You May Be Thinking About COVID-19 Risk All Wrong
Results Build on Other Research
The Penn State investigation is not the only laboratory investigation to assess the impact of mouthwashes and other oral rinses on coronavirus levels. Meyers says that his study supports findings published in October in The Journal of Infectious Diseases showing that certain types of oral rinses could inactivate SARS-CoV-2 (the coronavirus that causes COVID-19) in similar experimental conditions. Lab-based research from Cardiff University in Wales published in November in bioRxiv may add to the evidence supporting the benefits of mouthwash. The study, which has not yet been peer reviewed, found that mouthwashes containing at least 0.07 percent cetypyridinium chloride (CPC) reduced viral infectivity. CPC is an antimicrobial compound commonly used in over-the-counter mouthwashes and toothpastes to reduce plaque and tartar and promote gum health. A study published in the British Dental Journal in June suggested that good oral health practices that reduce the amount of bacteria in the mouth may help reduce COVID-19 symptoms such as respiratory infections. The authors recommend that “oral hygiene be maintained, if not improved, during a SARS-CoV-2 infection in order to reduce the bacterial load in the mouth and the potential risk of bacterial superinfection.” Because the mouth is a gateway through which bacteria and other germs can enter the respiratory system and blood stream, doctors have drawn a connection between oral health and overall health. The Mayo Clinic says that oral health might contribute to various diseases and conditions, including endocarditis (an infection of the inner lining of heart chambers or valves), cardiovascular disease, pregnancy and birth complications, diabetes, osteoporosis, and Alzheimer’s disease. RELATED: Your Blood Type May Affect Your COVID-19 Risk, Studies Suggest
How Much Could Mouthwash Really Help?
Meyers is the first to point out that gargling with mouthwash or using another kind of oral or nasal rinse isn’t going to cure COVID-19. “All the infected cells in your mouth are still going to have the virus,” he says. “But if we can knock down the viral load that’s coming out of the mouth or out of the nose by half or even more, that could be a very significant in lessening the spread.” Even if mouthwashes and rinses prove able to help curb coronavirus transmission, by no means should people let up when it comes to other protective actions. “Using a nasal rinse or mouthwash does not mean that you can safely kiss another person, avoid social distancing, or even stop wearing a mask,” Dr. Glatter says. “You must continue to practice these important public health measures.” Meyers agrees. “We’re not telling people to take off their masks or stop social distancing,” he says. “We’re just suggesting that there’s another layer that we could put on top of all this. Whether you use mouthwash for this or for just general oral hygiene, this study provides more evidence that this practice could be very positive for your health.”
