Finally! An expert answers what to do when you're not on the loo.
Bathroom etiquette runs the gamut from the nonnegotiable (put down the seat when you’re done, men!) to the debatable (should toilet paper roll over or under?). And one of the most disputed behaviors has to do with the unassuming toilet lid.
You may have heard that you’re supposed to close the toilet lid when flushing, but just how bad is it to keep it up when nobody is using the toilet? An uncovered toilet isn’t a home decor “do”—that’s for sure. But is it a health hazard?
As a science reporter, I love to uncover the places germs hide and discover crucial changes we need to make for our health (and the things that are just overkill). So I reached out to microbiologist Jason Tetro—better known as the Germ Guy—to find out if there’s any real harm in leaving the lid up. Keep reading to learn whether you should keep the lid on your toilet closed 24-7, or if a little air does a bowl good.
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Why should you keep the toilet lid closed when flushing?
There’s no delicate way to say this: If you flush with the lid up, poo and pee fly everywhere. Flushing the toilet creates a “toilet plume,” the scientific term for a spray of aerosolized droplets of bacteria and viruses. (If that’s not a hidden home danger, I don’t know what is.) When you flush with the lid up, “the aerosolized droplets can end up as far as 6 feet from the toilet,” says Tetro. “Shutting the lid before flushing can prevent these aerosols from getting out into the room.”
While it’s not a perfect precaution, it makes a real difference. A 2020 study sampled aerosols after flushing with the lid up and down and found that doing it lid-down slashed the bacteria-containing aerosols by up to 50%.
Should you keep the toilet lid open or closed when the toilet isn’t in use?
You should still keep the lid shut, even when the commode is not in use. Here’s why: “When the lid is closed, you are preventing a potential vehicle for spread,” Tetro says. “Although the majority of spread happens during the flush, there may still be residual bacterial contamination that could potentially be a problem.”
No matter how clean your home is, your toilet bowl is teeming with germs. Your porcelain bowl may contain viruses like norovirus, and bacterial pathogens including E. coli and C. difficile (aka C. diff). “Fecal coliforms like C. difficile can be opportunistic pathogens,” Tetro explains, “meaning they can cause infections in areas that are not used to seeing them or in people who are unable to fight them off.”
But wait a minute, you’re thinking. How can those germs fly around when I’m not using the toilet? The main route is via your pet. As pet owners know, dogs, and even some cats, treat the porcelain bowl like it’s their own fancy water station. That’s not a good thing for a couple of reasons. Lapping up contaminated water can give your pet a gastrointestinal infection. And it could make you sick through fecal transfer, Tetro says. If your pup slurps up E. coli-laced water and then licks your face, you’re at risk of getting sick.
So can you actually get sick from this?
Yes, this can definitely make you sick. If your dog transfers pathogens to your face or hands and they get in your mouth, you can contract a GI infection or norovirus. If the germs hit your mucous membranes or skin, you’re at risk of getting a bacterial skin, sinus or eye infection.
Is this a bigger problem if someone has a stomach bug?
If someone in your house has norovirus—a bug that causes vomiting and diarrhea—be super careful about shutting the lid. One of the ways norovirus spreads is through contaminated toilets, according to the Centers for Disease Control and Prevention (CDC). In addition to closing the lid after use, it’s super important to disinfect your toilet if anyone in your household is sick (more on how to do that below).
Are there any other reasons to keep the lid closed?
There’s another reason to put a lid on it: It might help control the humidity in your bathroom. When the lid is open, it can make the bathroom slightly more humid, Tetro says. Since high indoor humidity is linked to mold growth, it’s a good idea to limit that in any way you can—including by shutting the pot.
What are some other ways you can limit bacterial growth in your bathroom?
At this point, we can all agree the toilet lid belongs closed, right? But beyond that, there are some simple steps you can take to keep germs to a minimum (and avoid the dreaded toilet plume effect).
After pooping, double flush
A follow-up flush reduces the bacterial levels in your bowl, according to a study that compared E. coli levels in toilet water after one and two flushes. “It’s not perfect,” Tetro says of the extra step, “but it helps.”
Give bathroom surfaces a once-over
Using warm, soapy water or a household cleanser, wipe down your bathroom surfaces (counters, handles, the toilet seat and more) on the regular.
Disinfect the toilet—especially if someone in your house has a stomach virus
Once a week, clean your toilet with a product that kills germs, such as a bleach-based bathroom cleaner. If someone in your house has a stomach bug, it is especially important to follow the CDC’s instructions for disinfecting:
- Wear disposable gloves and wipe the bowl with paper towels, then throw them in a trash bag and seal it.
- Prepare a disinfectant solution by mixing 5 tablespoons of household bleach per gallon of water.
- Wash toilet surfaces with the disinfectant.
- Let the disinfectant sit for at least five minutes.
- Clean the area with soap and hot water.
De-germ bathroom surfaces weekly
Wipe surfaces with a household spray daily. Once a week, use a disinfectant product, such as a bleach-based bathroom spray, to de-germ the counters and other surfaces.
Be anal about hand-washing
After touching bathroom surfaces, be sure to wash your hands with soap and warm water. Purell does not kill norovirus, so it’s key to use soap instead of hand sanitizer.
Get your toothbrush out of the line of fire
Make sure to get that thing you brush your teeth with every night out of the “plume” path. Stash it in the medicine cabinet or move it to a shelf that’s more than 6 feet from the can. Don’t you feel better already?
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Sources:
- Jason Tetro, microbiologist, author of The Germ Code and The Germ Files, and host of the Super Awesome Science Show podcast; email interview, Nov. 10, 2025
- CDC: “How Norovirus Spreads”
- Journal of Environmental Health: “Persistence of Bowl Water Contamination during Sequential Flushes of Contaminated Toilets”
- CDC: “Mold”
- Access Microbiology: “Real-time Monitoring of Aerosols Generated from Toilet Flushing”
