Experts warn your toothbrush could be harbouring harmful germs
By BBC, October 21, 2025Bacteria from our toilets, the cold sore virus, and thrush-causing yeast can thrive on our toothbrushes. But there are ways to keep your toothbrush a little cleaner.
Your toothbrush is a disgusting miniature ecosystem. Its fraying bristles form an arid scrubland that each day is temporarily flooded, transforming it into a wetland awash with nutrients. Thriving among the thickets of towering plastic stalks are millions of organisms.
Also Watch: Did you know that it is important to wipe your baby’s gums even before growing teeth?
Right now your toothbrush is home to something like 1-12 million bacteria and fungi belonging to hundreds of different species, alongside countless viruses. They form biological films on the exposed surfaces of your brush, or worm their way into the fractured stalks of ageing bristles. A daily influx of water, saliva, skin cells and traces of food from our mouths give these microbes all they need to thrive. Every so often, they are joined by a shower of other microorganisms that arrive with the flush of a nearby toilet or opening of a window.
And twice a day you put this delightful cocktail into your mouth to give it a good stir around.
So, should you be more concerned about how clean your toothbrush is?
Also Watch: ” If partners always kiss, what’s the big deal sharing toothbrushes?” Of relationships and intimacy
It’s a question that has been troubling dentists and doctors for years, prompting them to examine just what is living on our toothbrushes, what risks those microbes pose and how we should be cleaning our tooth-scrubbing implements. (You can also learn more about how to properly brush your teeth according to science in this article by Martha Henriques.)
Where the microbes come from
“The microbes on toothbrushes primarily originate from three sources,” says Marc-Kevin Zinn, a microbiologist at Rhine-Waal University of Applied Sciences in Germany, who has studied the microbial contamination of toothbrushes. These are the user’s mouth, their skin and the environment where the toothbrush is kept.
But before we even use a toothbrush for the first time it can carry its own community of microbes. A study of 40 new toothbrushes from different manufacturers bought from stores in Brazil, for example, found half were already contaminated with a variety of bacteria.
Fortunately, most of the microbes found on our used toothbrushes are fairly harmless. The majority come, perhaps unsurprisingly, from our own mouths. Each time we pop the brush into our oral cavity, the bristles sweep up microbes such as Rothia denocariosa, Streptococcaceae mitisand members of the Actinomyces bacteria – all normally benign residents of our mouths. Some of those clinging to the bristles and toothbrush head can even be beneficial for our health, helping to protect us against other microbes that cause tooth decay.
But lurking amongst them are hitchhikers that do mean us harm.
Harmful bacteria
“The most important are Streptococci and Staphylococci, which cause tooth decay,” says Vinicius Pedrazzi, a professor of dentistry at the University of São Paulo in Brazil. Others can cause inflammation in our gums, known as periodontal disease.
Researchers have also found bacteria and fungi living on used toothbrushes that have no right to be there – organisms more commonly associated with stomach infections and food poisoning such as Escherichia coli, Pseudomonas aeruginosa, and Enterobacteria. Studies have also identified pathogens like Klebsiella pneumoniae – a common cause of hospital-acquired infections – and Candida yeasts, which can cause thrush, on toothbrushes.
These microbes come from the water we rinse our brushes with, our hands and other parts of the “environment”. But consider this – that environment is likely to be your bathroom.
How to clean your toothbrush
There is a bewildering array of techniques for sterilising toothbrushes, from using ultraviolet light to popping it in the dishwasher or microwave. Some of the least effective have been found to involve blasting your brush with a hairdryer or submerging it in a glass of whisky. The microwave is often found to be the most effective, but also risks melting or damaging the bristles of your toothbrush.
The toothpaste you use – which will often have antimicrobial properties – can do some of the work to reduce the number of microbes growing on your brush. Rinsing it in water also helps to flush some of the bacteria down the plug hole, but many bacteria still cling on and grow.
Some researchers recommend a solution of 1% vinegar as the most effective way of reducing bacteria, but it will leave a taste that some will find unpleasant when you next use your brush. Soaking the head of the brush in an antiseptic mouthwash solution for five to 10 minutes can also be effective.
A few researchers, however, are turning to a different approach – toothpastes that actually encourage bacterial growth. Probiotic toothpastes that aim to inoculate and encourage the growth of certain “friendly” bacteria that are known to be beneficial to oral health.
Streptococcus salivarius, for example, is known to help suppress harmful bacteria and fight plaque, and is being trialed by a company in New Zealand. Another, Limosilactobacillus reuteri strongly competes against Streptococcus mutans, potentially protecting against tooth decay.
“Concepts like probiotic coatings or bioactive bristle materials might offer innovative ways to promote a healthy microbial balance on toothbrushes, turning them into vectors of protection rather than risk,” says Zinn. But he cautions there is still a lot of research to be done in this area.
In the meantime, you might want to take a closer look at that brush in your bathroom. Is it time to replace it? Or perhaps just move it further away from the toilet.