Listerine Kills Gonorrhea Bacteria, But Please Don't Get Any Ideas

A nice blue gonorrhea-killing beverage (Getty Images)
A nice blue gonorrhea-killing beverage (Getty Images)

Scientists have concluded that mouthwash kills gonorrhea bacteria—in your mouth, that is. I can’t vouch for your other parts, but maybe don’t put mouthwash there.

Now you’re thinking the same thing that I did: okay, of course Listerine kills bacteria. Well, Listerine advertising from far back as 1879 said the product cured gonorrhea, according to Live Science. But the scientists behind this most recent study state that no one bothered to test the claim until now. The recent Centers for Disease Control and Prevention report showing an uptick in Americans with STDs, including 400,000 cases of gonorrhea, makes this is an especially good time to look for some bacteria-fighting help.

The team of Australian researchers tried a few tests. First, they added gonorrhea-causing Neisseria gonorrhoeae bacteria to Cool Mint and Total Care Listerine. They spread the mixtures on agar gel—bacteria food—and the Listerine-treated bacteria didn’t grow. Then, the team had 196 men who have sex with men, 58 of whom tested positive for a gonorrhea infection, gargle with the Listerine. Afterwards, the throats of only 52 percent of the infected men tested positive for gonorrhea, while 84 percent of those who slurped a saline solution tested positive. The study, published in the journal Sexually Transmitted Infections today, does not detail whether any kissing followed the swishathon.


Hearing that scientists are only now testing a thing you thought was always true should feel familiar. This past summer, the Associated Press showed that no one had really bothered to test how well another part of the daily dental routine worked: flossing. That story ended the same way this one will: there’s definitely more research to be done.

196 people really isn’t that big of a sample size. The gargle also only seemed effective at killing bacteria on the tonsils, not deeper in the throat, and the researchers didn’t do a long term study to see whether the gonorrhea stayed dead.

Either way, keep using mouthwash, you get me?

[Sexually Transmitted Infections via Live Science]


Former Gizmodo physics writer and founder of Birdmodo, now a science communicator specializing in quantum computing and birds

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196 people really isn’t that big of a sample size

Could you “science” writers please learn what a sufficient sample size for fuck’s sake?

With these estimates we would need about 30 individuals in each arm or about 60 culture positive individuals in total at 80% power with a two-side significance level of α=0.05.

They took into account the necessary sample size they need. Massive sample sizes with several hundred people or even a few thousand people are not necessary for this sort of research. You need massive samples for polling/surveys to ensure you have an accurate cross-section of respondents and for clinical studies to be 99.9999% sure a medication is safe and effective, but not for too much else.

I’m so tired of seeing so people with absolutely no experimental research experience making comments like this. Every Gizmodo post on a study, every reddit thread, everywhere. Sample size is totally dependent on what sort of effects you’re investigating and how you’re investigating it.

I want to make a disclaimer that I’m not a biology research so who knows, maybe the sample size is too small even though the researchers explicitly stated that they computed their power beforehand. But I’m so tired of seeing it even on cognitive psych studies with more than 30 participants and fMRI studies with more than 15 participants. In behavioral studies, researchers aren’t recruiting 2000 participants to complete a single-trial task like in clinical research, they’re recruiting 30 participants to complete dozens or hundreds of trials in a task. In fMRI studies, a single participant might be completing a few hundred trials, and during each trial, the MRI will record the blood oxygenation level of a million goddamn voxels.