In the grand scheme of things, two and half years isn’t that long ago — but in the timeline of COVID-19, it’s a lifetime ago. Experts have learned a lot about the virus and its treatments since that time. Additionally, our pandemic world looks completely different than it did then.
Back in 2021, a few studies and meta-analyses looked into the use of mouthwash as a potential way to decrease your risk of spreading and catching COVID-19. The results were mixed, but there was some evidence that mouthwash could reduce the amount of virus in your mouth.
Anecdotally in our own lives, some people also mentioned that they use this method when they travel to help ward off illness. And when you’re in close quarters like an airplane, it can feel really tempting to do everything possible to stay healthy before, during and after a big trip.
So, what do experts think of using mouthwash to protect you from getting COVID-19? Should you reach for some mouthwash the next time you’re getting on a plane? Sadly no, probably not. Here’s why:
Since most of these studies are done in a lab, it’s hard to know the real-world implications.
“Many of these studies are done most often in a petri dish or in a lab,” said Dr. Nicholas Rowan, the clinic director of otolaryngology at Johns Hopkins Medicine.
While you can take a substance that is theoretically toxic to the virus and kill the virus in a lab or petri dish, it’s much harder to measure these results in the real world. So, it’s also hard to understand how effective something like mouthwash as a COVID mitigation strategy can be, according to Rowan.
“I think this is a trend that we see over and over again in science … just because something worked in a lab, in a very controlled experiment, doesn’t always mean it’s going to translate into the real world,” said Chana Davis, a geneticist and science communicator at Those Nerdy Girls. “And this just really hasn’t yet been proven to move the needle in the real world.”
While most studies have taken place in a lab, research from this year actually measured results in people with a COVID-19 infection.
“There is one trial that was done in people that had COVID … they found a modest decrease in viral levels in the mouth, but with unclear clinical implications,” Davis said.
The study itself stated that “further studies are needed to corroborate these results and investigate whether the observed reductions in viral load and infectivity could translate into clinically useful effects in reducing COVID-19 transmission.”
“So, it can kill some of the virus in your mouth, but that doesn’t mean you’re not teeming with virus elsewhere in your body, right?” Davis added. In other words, even if the virus load decreases in your mouth temporarily, you can still sneeze or cough and spread COVID-19 on to others.
“The issue is … that most transmission is through your exhaled breath, and so by washing your mouth, you’re not getting rid of the virus in your lungs that you’re then exhaling into the world,” Davis explained.
Additionally, even if you use mouthwash after sitting next to someone on a plane who’s coughing, for example, you can still breathe in their virus particles and get sick. Mouthwash is not going to protect you from that.
So, with that being said, it’s premature to say mouthwash as a COVID mitigation strategy is a proven prevention method.
“It’s hard without having kind of rigorous study behind it to say that it is something that I’m putting my name behind as a physician saying, you’ve got to do this,” Rowan said.
From the pandemic, we’ve learned that high levels of evidence are necessary when considering any new science, Rowan added. This is just not the case with these mouthwash studies.
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Nasal sprays have more evidence behind them, although more research needs to be conducted there as well.
In 2021, Rowan and a team of experts published a study about the “non-pharmacologic interventions that can be used to reduce respiratory viral transmission,” he said.
The research looked at nasal washing, gargling, personal protection equipment like masks, social distancing and hygiene.
“Gargling, again, is kind of one of those categories with little downside, but probably little potential upside,” Rowan said.
Interestingly, there was higher evidence behind nasal washing: “cleaning out your nose to actually physically get some of the stuff out, which also helps in your symptoms,” Rowan said. In Rowan’s research, saline nasal wash was studied.
Davis said that sprays with a nitric acid base — which is different from what Rowan studied — tend to be most effective.
“There is some actual real-world evidence that they can potentially move the needle on your infection risk, and I think that also has plausibility if the nasal root is a main passageway for entry,” Davis said. “The spray turns into nitric acid, which is a known antiviral.”
She added that this kind of spray is approved in certain countries, but not yet in the United States or Canada.
All in all, more research is needed to determine the efficacy of nasal sprays for COVID-19 transmission, and what kind of nasal spray actually works best. But, experts say it does sound much more promising than mouthwash.
In the end, focus on the strategies that we know work.
The strategies we’ve used for the past few years to stay healthy and keep those around us healthy are what you should be turning toward — not mouthwash.
“Wash your hands if you’re not feeling well then stay home. If you’re coughing, sneezing, having some symptoms then wear a mask [and] if you’re in environments where you’re worried about potential exposures, then masking is a great idea,” Rowan said.
Specifically, N95 and KN95 masks offer the best protection, which is paramount for someone in close quarters like an airplane.
When it comes to using mouthwash, it certainly can’t hurt (and your dentist will likely thank you) but it should not be the only way you are protecting yourself and loved ones from COVID-19.
“It’s easy to support something that is essentially a low to no risk to the patient … perhaps maybe there’s a little bit of discomfort from stinging in the mouth when using a mouthwash, people don’t like the taste of it,” Rowan said. “So, that list of side effects is pretty minimal but the potential upside is probably also, generally, little to none.”
