Shocking but true: your toothbrush is dirtier than your toilet seat. It is hard to predict exactly which germs are on your toothbrush right now, but staphylococci, coliforms, pseudomonads, streptococci, and at least one fungus, candida, have all been cultured from used toothbrushes.
In one Australian study, staphylococci and streptococci were the most commonly found pathogens on used toothbrushes. Even if you have a brand-new toothbrush, it gets contaminated the first time you use it.
Since the purpose of brushing is to remove bacteria that cause gum disease and tooth decay, it could conceivably be self-defeating to use a contaminated toothbrush, you’d be reinoculating yourself every time you brushed. But it isn’t clear how much of a danger this poses in the real life of a healthy person.
How long the microbes survive on your brush varies, anaerobic germs tend to die unless they have some hollow space in the brush where they can thrive. Most plastic brushes have no such hiding places, but the handle of an electric toothbrush was found in one case to provide the right airless environment for Porphyromonas gingivalis, a germ that causes gum disease, to live happily.
This same study found on used toothbrushes Streptococcus mutans and, most persistently, Candida albicans, a very common fungus that most people live happily with but that can cause mouth sores and vaginitis and sometimes, usually in the immunocompromised, systemic illnesses that can be fatal. Most toothbrush germs are gone within 24 hours if the toothbrush dries out.
Finding these organisms on toothbrushes shouldn’t be surprising, they are among the most common germs we all live with, and unless you are elderly, pregnant, or immunocompromised, they’re usually harmless.
For most people, the advice to shake the water off your toothbrush and let it dry will be sufficient to prevent any serious threat. For those who want to be extra careful, soaking a toothbrush for 20 minutes in Listerine eliminates most germs the brush might harbor.
How about the bath mat? There are several studies that document the presence of bacteria and fungi in carpeting, but there isn’t any evidence that their presence there causes any increase in infection rates. A clean bath mat will attain a certain level of contamination fairly quickly and stay at that level until it is washed.
After washing, the bacterial count goes down and then quickly rises again. A wet mat is a better place for bacteria to grow than a dry one. Sanitizing your bath mat or any other laundry is probably not essential to good health, but if you really want to, there are ways to do it.