Right now, on a counter somewhere in your house, there’s a toothbrush waiting for you. And there’s a very good chance it’s carrying more bacteria than the toilet seat a few feet away from it. That isn’t a scare line for clicks. It is what researchers at the University of Manchester in England found when they tested real toothbrushes: a single uncovered brush can carry more than 100 million bacteria, including E. coli (the kind that gives you diarrhea) and staph (the kind that causes skin infections).
For comparison, the average toilet seat has about 50 bacteria per square inch. Your toothbrush isn’t in the same league. It isn’t even in the same sport. You can scrub it, boil it, run it through the dishwasher, or buy a UV sanitizer, but you still won’t fix the real problem. The issue isn’t what is on the brush. It is where the brush is sitting.
The Invisible Cloud on Your Counter
In 2022, a team of engineers at the University of Colorado Boulder, led by Professor John Crimaldi, used high-powered green lasers to film what happens when a toilet flushes. The results, published in Scientific Reports, revealed that every flush with the lid up fires off a cloud of tiny water droplets invisible to the naked eye. The team clocked these droplets moving at over 6.6 feet per second, reaching nearly 5 feet above the bowl in just 8 seconds. Crimaldi described the ejection as coming out “like a rocket,” not merely drifting or misting. This phenomenon, known as the toilet plume, can reach up to six feet from the bowl. In a standard bathroom, this places almost everything on the counter inside the splash zone. The plume carries fecal bacteria, norovirus, and traces of the virus causing COVID. A separate study by researcher Lauren Aber at Quinnipiac University found that more than half of toothbrushes in shared bathrooms had fecal matter on them, with an 80% chance the bacteria came from someone else in the house.
Related: Kitchen Clutter Solved Hide Bins in One Spot
The instinct to clean the brush is natural, but attempts to scrub, boil, microwave, soak in mouthwash or hydrogen peroxide, or use plastic caps are useless or harmful. Sanitizers may kill 99.9% of bacteria, but with tens of millions present, hundreds of thousands remain, and no study proves these gadgets prevent sickness. Plastic covers and closed containers are actively worse. The American Dental Association states that storing a moist toothbrush in a closed container promotes microbial growth more than open air. A plastic cover traps water, effectively building a tiny warm greenhouse for bacteria. The Manchester study confirmed that covered brushes grow more yeast and germs, not less.
Sources: American Dental Association; Crimaldi et al., Scientific Reports (2022); University of Colorado Boulder; Aber, Quinnipiac University (2015); University of Manchester.
