You Don't Want to Know What's Lurking on Your Toothbrush

Share a bathroom? You may be sharing more than just a sink, according to a new study. (Photo: Getty Images)

Your toothbrush may be in desperate need of a bath — and not just because of the crud it’s cleaning off your teeth. When Quinnipiac University researchers tested 71 toothbrushes of college students using communal bathrooms, they found that more than half were contaminated with fecal bacteria, according to a new study presented at the annual meeting for the American Society for Microbiology.

Although the study participants were sharing a bathroom with several people  — about nine, on average — you’re still at risk of bacterial transmission if you’re spitting into the same sink as just a few family members, study author Lauren Aber tells Yahoo Health. “You don’t think of it as a problem when they’re your family members,” she says. But, “it doesn’t really matter who the people are — you’re still sharing the [bacterial] flora. The results are most likely relevant to any situation where there’s a shared bathroom.”

In fact, in a home setting, there may be even more opportunity for germ swapping, since your toothbrushes are probably perched in the same holder. “That can allow for lateral transfer of bacteria, because toothbrushes could get knocked together or water sprayed in between brushes,” Aber says.

So how does fecal bacteria land on your bristles in the first place? Blame the force of your toilet’s flushing. When fresh water comes rushing into the toilet bowl, germs can go airborne, flying as far as six to nine feet, says Aber.

Related: How to Make Flossing a Habit

And de-germing your toothbrush isn’t as simple as rinsing it off. In the study, people’s attempts at decontaminating their toothbrushes consistently failed: Every toothbrush that had been rinsed in mouthwash was still coated in fecal coliforms — that is, any type of enteric bacteria, such as salmonella and E. coli.

Why didn’t the mouthwash do the job? “It could have been the length of time students were rinsing their toothbrush in mouthwash, or potentially the content of the mouthwash,” says Aber. (Past research has shown that soaking a toothbrush in Listerine for 20 minutes before and after use can, in fact, decrease the microbial contamination.) Rinsing the brushes in hot or cold water was no more effective, the study found.

As disgusting as the thought of fecal bacteria on your toothbrush is, the threat to your health is probably minimal. “Most of the bacteria we’re looking at — you would need a lot of it on your toothbrush to actually become sick from it,” Aber says. However, her study didn’t look at viral contamination, which could be more serious in small amounts. “You need very few viral particles for transmission of something like norovirus, the stomach bug that’s spread on cruise ships,” she notes. “And if you’re sick with any type of stomach bug, you’re going to be excreting it through the fecal matter.”

Related: The Gross Truth About How Often We Actually Brush Our Teeth

To shield your toothbrush from poop particles, place it inside your medicine cabinet, ideally in an upright position, between each use — or just put down the lid on the toilet when you flush. And skip the plastic toothbrush cases, which “actually allow and promote bacterial growth” since they keep the bristles moist, says Aber. To reduce the amount of bacteria you introduce to your mouth, allow your toothbrush to air-dry before using it again, the American Dental Association (ADA) advises.

The ADA also recommends replacing your toothbrush every three to four months — or sooner if the bristles become frayed — and Aber suggests tossing your toothbrush whenever you contract an oral illness, like the common cold or strep throat. To clean your bristles in between brushes, try using an ultraviolet (UV) sanitizer, she says, such as the Zapi UV Toothbrush Sanitizer. In a 2014 study, researchers in India found that placing a toothbrush in a UV-light holder for seven minutes dramatically reduced the bacterial load.

Read this next: Those White Streaks on Your Teeth? Blame Your Water

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