Why you shouldn't leave your toothbrush out on the sink
Would you lick your toilet? Of course not, but if you leave your toothbrush out you're doing the next grossest thing. After all, a toothbrush that sits out in the open in your bathroom can easily come in contact with all kinds of bacteria.
How your toothbrush gets dirty
If you're toothbrush is sitting out or in a cup on the sink, it can easily be knocked to the floor, the bathroom sink counter top or any number of bacteria-rich surfaces. If it's too close to the sink, your toothbrush could also be splashed when you wash your hands. The worst-case scenario is if a toilet flushed with the lid up sprays bacteria onto your toothbrush. According to Mental Floss, flushing with the lid up aerosolizes whatever has been flushed away. Anything within a five foot radius of your toilet will have some of that bacteria on it. If you go to the bathroom, flush with the lid up, and then go to brush your teeth, you're basically brushing with fecal matter.
What may be on your toothbrush
While the type of bacteria that can land on your toothbrush varies, E. coli would probably be one of the most prevalent. E. coli is a bacteria that lives in the intestines of people and animals. While many strains are harmless, some can cause major gastrointestinal problems including severe and sometimes bloody diarrhea, vomiting, cramping and other stomach and gut pain, according to the Mayo Clinic. Other bacteria that can be on your toothbrush can include lactobacillus, pseudomonas and several different types of staphylococcus. In addition to bacteria, fungus and viruses can also find their way to your toothbrush.
What you can do to keep your toothbrush clean
Luckily, keeping your toothbrush clean is not difficult. In most cases all you have to do is take it out of the bathroom. Just be sure wherever you put it is clean. If taking something you use in the bathroom out of the bathroom sounds silly to you, consider putting your toothbrush in a case case or placing it inside a medicine cabinet or bathroom cupboard. Just putting it somewhere else wont keep it entirely clean, however. At some point, bacteria is going to make it onto your toothbrush. That's why it's a good idea to soak your toothbrush in peroxide or mouthwash occasionally to attack bacteria and any other nasty stuff growing on it.