New research shows that certain types of mouthwash have the potential to reduce the viral load of COVID-19 in your mouth. But how long does this protection last, and are there other implications on your oral health to consider? This dentist breaks down the science and shares what we should really be doing.
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A newly published study shows that two types of mouthwash will reduce the viral load of COVID-19 in your mouth. Researchers at Rutgers University found that Listerine (an over-the-counter mouthwash) and chlorhexidine (a prescription antiseptic mouthwash) provided the best protection against the viral transmission of the coronavirus.

Though the study was done in a lab and still needs to be replicated in humans, for many people, this is one more perk of their mouthwash habit. However, the practice was already happening in dental offices around the country. Ever wonder why your dentist or dental hygienist may ask you to rinse with a mouthwash before even getting into the chair? "During the COVID era, a very strong mouthwash is recommended because it lowers the viral count in your mouth so when [your dentist] creates an aerosol—by drilling or polishing your teeth—they're better protected," says Mark Burhenne, D.D.S., a general dentist and co-creator of Ask the Dentist. (You can also find him on TikTok @askthedentist.)

So, while this research does indicate that mouthwash will reduce the viral load of COVID in your mouth, Burhenne adds that using it this way causes unwanted side effects. "Those benefits will only last for about 10 to 15 minutes and then [the mouthwash] will disrupt your mouth microbiome after that," he says. That's because an antiseptic mouthwash doesn't just kill COVID-19 pathogens—it kills all of the bacteria in your mouth. At least in the short term.

Shortly after using mouthwash, the bacteria in your mouth start to grow back. "The problem is that anaerobic bacteria grow back faster than the aerobic bacteria—and anaerobic bacteria are more pathogenic, or more capable of causing disease," says Burhenne. So now your mouth microbiome has an imbalance of bacteria (scientists call this dysbiosis) with higher levels of disease-causing bacteria than disease-protecting bacteria. Repeat this daily, and you can see how your oral microbiome can get out of balance.

The Connection Between Your Oral Microbiome and Your Overall Health

But why exactly is your oral microbiome important? The bacteria in your mouth help form the biofilm on your teeth. While this biofilm can interact with the carbohydrates you eat and create an acidic environment that harms your teeth (particularly if not removed through good brushing and flossing), biofilm can also be helpful for your oral health. Think of the biofilm as the skin of your tooth. This built-in system is there to help re-mineralize the tooth surface when needed, says Burhenne.

Also, your oral microbiome isn't just important for the health of your mouth. It plays a role in your overall health, just as your gut microbiome does. "Your oral microbiome feeds your gut microbiome," says Burhenne.

How Mouthwash May Impact Your Health

Using mouthwash can be problematic in other ways. Regular mouthwash use can actually cause bad breath—the opposite of what you'd expect—as well as increase your chances of developing cavities and gum disease, according to Burhenne. Research shows that using mouthwash can also raise blood pressure, and increase your risk of developing diabetes.

One study of nearly 1,000 overweight adults, published in the journal Nitric Oxide, found that those who used mouthwash two times a day (or more) had a 55% higher risk of developing prediabetes or diabetes compared to less-frequent users. That said, even once-a-day-mouthwash-users raised the risk. The researchers believe that this is due to the effects of mouthwash on the oral microbiome, as oral bacteria plays a role in nitric oxide, a compound that affects blood vessels.

Bottom Line

Burhenne advises against using mouthwash on the regular. Plus, keep in mind that swishing with mouthwash doesn't accomplish as much as proper brushing does, he says. That extra effort is what you need to keep your teeth clean.