Dr. Meyers said he hoped his team would undertake such studies soon, and noted that a handful of clinical trials had already begun investigating these questions.
The study’s findings aren’t necessarily surprising, or even unprecedented. Other researchers have conducted similar experiments, including one that looked at the effects of mouthwash on the new coronavirus, with comparable results. And since the early days of the pandemic, scientists have stressed the effectiveness of hand-washing and disinfection with soap, alcohol and other similar chemicals that can bust through the new coronavirus’s fragile outer layer, or envelope. (Not all mouthwashes or nasal rinses contain such potent ingredients, however.)
Dr. Valerie Fitzhugh, a pathologist at Rutgers University, pointed to a study from the 1990s, in which researchers in Texas inactivated a strain of flu virus by swirling it in Listerine for 30 seconds. But that study “was never shown to be clinically relevant,” she said.
Even if people did a very thorough job coating the inside of their mouths or noses with a coronavirus-killing chemical, a substantial amount of the virus would still remain in the body. The new coronavirus infiltrates not only the mouth and nose, but also the deep throat and lungs, where mouthwash and nasal washes hopefully never enter.
Viruses that have already hidden away inside cells will also be shielded from the fast-acting chemicals found in these products. “It’s not like your cells get infected and then they secrete a bunch of virus and they’re done,” Dr. Rasmussen said. “Infected cells are constantly making more virus. It’s a timing issue.”
Relying on mouthwash or a nasal rinse to rid the body of infectious virus would be about as futile as trimming the top of a cluster of weeds, paying the roots little mind, and expecting the garden pests to disappear.
Dr. Meyers acknowledged this limitation. After a quick swizzle of mouthwash, “How long do you have? I don’t know,” he said. “All we’re saying right now is, this could add an extra layer of protection,” he explained, on top of proven protective measures like mask-wearing and physical distancing.