It’s trending on social media and generating excited media reports – another study showing an ingredient found in mouthwash can kill the coronavirus. In this case, it’s as fast as 30 seconds.
But mouthwash is unlikely to ever be a solution to the pandemic, or even someone’s own personal protection plan.
That’s because many things can kill a virus on contact, but they’re not going to stop the source of the virus.
“Yes. There is some data out there – I am not saying it’s great data – that fill-in-the-blank substance inactivates or inhibits replication of coronavirus,” Dr. Graham Snyder, associate professor in the Division of Infectious Diseases at the University of Pittsburgh School of Medicine, told CNN.
Alcohol, chlorhexidine, hydrogen peroxide and a range of other compounds can all kill viruses on contact or shortly after.
But none of the studies recently released on preprint servers shows they can reduce the risk of either catching or transmitting the virus, Snyder points out.
Inside the human body, the virus is constantly replicating in the upper respiratory tract – in the nose, the sinuses, the throat, bronchial tubes and lungs.
“It is still in your nose, in the fluid on your vocal cords, and in your lung airways,” said Dr. Donald Milton, who studies the transmission of viruses at the University of Maryland.
“All of these and especially the vocal cords and lung airways are major sources of the virus in the air,” Milton told CNN.
“You can’t sterilize your mouth
“When we exhale, cough, sneeze or what have you, virus could be coming from any of those places,” Snyder said.
While using a mouthwash or some kind of oral rinse could in theory reduce the amount of virus or bacteria in someone’s mouth for a short period, it’s not possible to sterilize a human mouth, and any microbe will grow back again in a fairly short time.
“You can’t sterilize your mouth. It is never going to be totally free of pathogens,” Snyder said.
“Using these oral rinses won’t substantially stop the disease process. The virus will continue to replicate.”
The same goes for ultraviolet light,” Snyder noted. While UV light from any source – the sun, a sunlamp or many of the anti-coronavirus devices hitting the market – can kill the virus on surfaces, they cannot get inside the human body and they cannot stop more virus from landing later and they cannot stop someone from exhaling more virus seconds after they’ve been irradiated.
Mouthwash or other disinfectants also will do little to protect someone from inhaling virus, said Dr. Leana Wen, emergency physician and Visiting Professor of Health Policy and Management at the George Washington University School of Public Health.
Hand sanitizer in the nose?
“The virus can enter our respiratory system in two ways. It can enter through contact, for example, if you touch a doorknob that someone else just touched who has coronavirus, then you touch your nose, mouth, or eyes,” Wen said.
“It can also enter through inhalation, when you breathe the same air as someone who is contagious. Washing your mouth or nose won’t prevent the virus from being breathed in. But wearing a mask does–and so does keeping good physical distance.”
Wen said she’s had to recently explain why applying Purell to the nose – something that sounds uncomfortable and dangerous as well as useless – won’t protect anyone from infection.
It’s such a tenuous theory that even Johnson & Johnson, makers of Listerine mouthwash, have explicitly warned consumers against the idea.
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“Listerine mouthwash has not been tested against any strains of coronavirus,” the company said on its website.
“Only some Listerine mouthwash formulations contain alcohol, and if present is only around 20% alcohol. Listerine mouthwash is not intended to be used, nor would it be beneficial as a hand sanitizer or surface disinfectant.”