September 23, 2025, 5:15 am | Read time: 4 minutes
For many, the bathroom is considered the cleanest place in the house. After all, it’s the room where people freshen up daily. Yet, precisely where hygiene should be paramount, invisible dangers lurk: bacteria and germs. A particularly common hygiene mistake that spreads germs in the bathroom arises from improper toilet flushing.
It’s actually a simple action, but it can determine whether you spread germs in the bathroom when flushing the toilet. The key is closing the toilet lid. “There are studies that clearly show that microorganisms from the toilet can be found on other surfaces in the bathroom through aerosols formed during flushing,” confirms microbiologist Dirk Bockmühl when asked by myHOMEBOOK. A 2022 study shows how quickly and far germs are propelled into the air from the toilet.
Overview
Study Confirms: How Unhygienic Flushing With an Open Lid Really Is
Although it’s known that aerosols can carry pathogens such as E. coli and noroviruses, the danger they pose is still underestimated. This is not only true when coughing into one’s hand but also when flushing the toilet, which also disperses aerosols—and thus germs—in the bathroom. This can be prevented by closing the toilet lid. Yet many leave the lid up, thinking it can’t be that bad, right? Wrong!
“If it’s something you can’t see, it’s easy to pretend it doesn’t exist,” says John Crimaldi, professor of civil, environmental, and architectural engineering at the University of Colorado Boulder. That’s why Crimaldi and his research team made the aerosols visible with laser light in a study that shows how aerosols are propelled into the air during a toilet flush.
The results dramatically show how quickly and far particles are ejected from the toilet. During flushing, droplets reach a speed of two meters per second, and within eight seconds, they rise to a height of one and a half meters above the toilet. But that’s not all. As the study describes, larger droplets settle on bathroom surfaces in no time. It’s different with aerosols, the smaller particles. They remain airborne for several minutes after flushing.
Pathogens on Toothbrushes, Too?
The aerosols, or tiny droplets, eventually settle on surfaces and objects. In the bathroom, this can quickly include the toothbrush. Microbiologist Bockmühl warns: “In principle, germs are found everywhere, especially where it’s damp. Besides drains, this is also true for toothbrushes. Since direct ingestion of pathogens is possible from there, it’s particularly important to let the toothbrush dry as quickly and thoroughly as possible and to replace it regularly, especially after infections.”
How Can You Prevent the Spread of Germs When Flushing the Toilet?
To prevent germs from spreading when flushing the toilet, it’s clear: Close the toilet lid before flushing. This is also recommended by Chinese virologists in a hygiene study. Dirk Bockmühl also explains to myHOMEBOOK that this is the best solution to prevent the spread of germs from the toilet. However, he notes: “Even though it doesn’t completely stop the spread, significantly fewer pathogens reach other areas in the bathroom, especially during family infections.”
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Expert Tip: Fresh Air in the Bathroom
Not only is the spread of germs when flushing the toilet a problem. Bacteria and viruses thrive in a warm environment. After showering, the bathroom is usually damp. In a damp bathroom, mold is also an issue. That’s why the tiles should be thoroughly dried after showering, as Bockmühl explains.
How else can you get rid of pathogens in the bathroom? With fresh air. Bockmühl says: “What you should definitely ensure is adequate ventilation. This provides air exchange and primarily removes moisture from the bathroom, which significantly influences germ growth and the survival of microorganisms.”
Is Disinfecting Surfaces in the Bathroom Worthwhile?
Disinfecting surfaces in the bathroom—you can do it, but it’s not necessarily required. Pathogens among the germs only slightly escape from the toilet after flushing, explains Bockmühl. And he reassures: 99 percent of germs are killed by conventional toilet cleaners: “There’s no danger there.”
Microbiologist Bockmühl adds: “An exception might be during an acute gastrointestinal infection in the family. In this case, additional disinfection might help reduce the risk of infection for other family members.”