Please Ignore the ‘Mouthwash Kills COVID’ Story

This is an absolutely head-spinning time for medical news, with new studies getting published online and then written up by 10 outlets before anyone has validated them—like the Tuesday morning headlines, amplified by Twitter, trumpeting the apparent COVID-fighting power of mouthwash based on a single study from Cardiff University. The headlines specify that the COVID-fighting is taking place specifically in the mouth, but is delightfully ambiguous about what role that has in fighting or preventing a COVID infection overall.

Of course, jokes about the fact that Listerine can obviously “kill COVID,” given that it could probably strip the paint off of a submarine if you poured a bottle into the ocean, are all in good fun.

But, especially since people have already tried their hand at some messed-up, scammy, at-home COVID cures over the course of the pandemic, we should be careful what we say when it comes to “treating,” “curing,” or “killing” the virus that’s keeping many of us from heading home for the holidays.

First of all, according to infectious disease epidemiologist Saskia Popescu, the very conditions the study in question was conducted under should give people pause before they extrapolate out the results. “The study that was done at Cardiff University is in vitro, meaning in a lab, and showed some evidence that mouthwashes containing 0.07% or more cetylpyridinium chloride (CPC) could kill the virus that causes COVID-19 when exposed to it,” Popescu said. “This is great, but has a lot of serious limitations we need to remember: It’s in a lab, so not real-life with real people.” 

Does this mean we need to toss the results of the study completely? Not at all. It simply means that it represents yet another data point in the sea of not-so-conclusive information we’ve gathered over the last (ugh) year about how the virus that causes COVID-19 lives and dies. 

“It’s not unlikely that some chemicals in mouthwash, especially something like alcohol, would inactivate SARS-CoV-2, but this is very preliminary data and ultimately doesn’t impact that much in terms of reducing transmission,” Popescu said. “While [these properties] could help reduce viral load/burden within saliva, it wouldn’t impact the respiratory tract or lungs where the virus is also present.” 

Popescu strongly cautioned against using mouthwash for COVID-related reasons… or for anything beyond its intended purpose. “This in particular is important for people to understand as it’s also crucial they don’t try to ingest or inhale mouthwash, which could get them sick,” she said. “People still need to wear a mask, distance, limit time indoors with those outside their household, wash their hands, etc.” So please, for the love of all that’s Scientific, do not go out and buy mouthwash for any reason that you wouldn’t have done so yesterday. 

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