Kids’ Sports Mouthguards Crawling With Dirt Bacteria, Rinsing With Water Barely Helps

That sticky, grimy mouthguard shoved into a backpack after football practice might seem like a minor parenting headache. But a new study found that most of the bacteria on children’s mouthguards don’t come from the kids’ mouths. Instead, these devices pick up bugs from the environment: soil, grass, and whatever surfaces they touch between games. And once those bacteria settle into a well-worn mouthguard, a quick rinse under the tap does far less than it seems.

Researchers at Australia’s Swinburne University of Technology, writing in the journal BMC Oral Health, collected mouthguards, storage cases, and mouth swabs from ten boys on a junior Australian Football League team, all under age 12. The mouthguards and their cases were teeming with bacteria typically found in soil, water, and on plants, organisms that had nothing to do with the kids’ normal mouth bacteria. Meanwhile, the surfaces of used mouthguards had become so worn and roughened from a season of biting, clenching, and impact that they had become bacterial welcome mats.

Brushing a mouthguard with a toothbrush and toothpaste wiped out almost all of that bacteria in laboratory testing. A simple rinse under the tap, the method most manufacturers recommend, left a large share behind. That gap could matter for kids whose chewed-up mouthguards are harboring bacteria capable of forming stubborn, hard-to-remove colonies.

Mouthguard Bacteria Are Coming From Dirt, Not Kids’ Mouths

To find the source, the team swabbed the inner and outer surfaces of each mouthguard, the insides of storage cases, and the players’ mouths, collecting the samples right before a scheduled training session. They grew whatever bacteria they could from those swabs and identified the organisms using genetic sequencing, a technique that reads a signature stretch of bacterial DNA like a barcode to figure out which species are present.

They found 38 distinct bacterial strains spanning 13 different groups. The most common organism was Pseudomonas putida, a species commonly found in soil and water but not in mouths. Most of the bacteria pulled from the mouthguards and their cases were environmental species tied to dirt, plants, and water. The kids’ mouth swabs told a very different story, showing only two main bacterial groups that are normal residents of the human mouth.

That mismatch is the study’s most telling detail. It suggests much of the contamination likely happens during the handling and storage that bookend each practice and game, rather than while the mouthguard sits in a child’s mouth. Mouthguards dropped on the ground, stuffed into cases with dirty hands, or left sitting in warm, moist containers between uses are apparently picking up hitchhikers from the surrounding environment. (Culture-based methods capture only a fraction of all bacteria potentially present, so small numbers of oral bacteria may also live on the devices without being detected here.)

Storage cases turned out to be part of the problem rather than a safeguard. Bacteria pulled from the cases showed an even stronger ability to form resilient colonies than the bacteria on the mouthguards themselves. One species found in a storage case, Klebsiella oxytoca, formed colonies nearly seven times more readily than the benchmark strain the researchers used for comparison.

Several other species from the cases also formed robust colonies, a sign that poorly maintained cases can act as reservoirs for bacterial growth rather than protective containers. A warm, moist, enclosed snap-shut case is apparently hospitable to bacteria introduced through dirty hands or contact with grassy, muddy playing surfaces. Cleaning the cases, not just the mouthguards, matters too.

One Season of Play Makes Mouthguard Bacteria Worse

Beyond identifying what was growing on these devices, the researchers wanted to understand why bacteria clung so effectively to used mouthguards. They examined the surfaces of new and used mouthguards using advanced imaging tools that build detailed three-dimensional maps of a surface’s texture.

Differences between the two were dramatic. A brand-new mouthguard scored a surface roughness of about 0.7, almost perfectly smooth. A mouthguard collected after one season of play came in at roughly 174, more than 200 times rougher. Months of biting, clenching, and repeated impacts had chewed grooves, pits, and ridges into the once-smooth material.

To test whether that roughness actually mattered for bacterial growth, the team created artificially roughened surfaces that mimicked the texture of a used mouthguard. They then exposed both smooth and rough surfaces to Pseudomonas putida and tracked how many bacteria latched on over time. Within the first hour, the roughened surfaces had roughly eight times as many bacteria attached as the smooth ones. Even after 48 hours, rough surfaces held about six times the bacterial load.

Microscope images confirmed the pattern. On smooth surfaces, bacteria appeared as scattered, isolated specks. On roughened surfaces, dense clusters had settled into the crevices and grooves, hiding in tiny sheltered pockets where they could thrive undisturbed.

Worn surfaces had also become more water-attracting, a property that further encourages bacteria to stick. New surfaces repelled water more effectively, while used ones let water spread and cling, creating a friendlier environment for bacterial growth.

A Toothbrush Beats Every Other Mouthguard Cleaning Method

Armed with evidence that used mouthguards are bacterial hotspots, the research team tested six common cleaning approaches: a cold water rinse, a warm water rinse, an alcohol-based mouthwash, a hydrogen peroxide mouthwash, a denture-cleaning tablet dissolved in water, and manual brushing with a soft toothbrush and fluoride toothpaste.

Each method was applied to mouthguard material, both smooth and roughened, contaminated with Pseudomonas putida, the most common species found in the study. Researchers then counted the remaining bacteria and compared them with uncleaned samples. (These cleaning tests used a single representative species rather than every bacterium identified, so results may vary for other organisms.)

Brushing with toothpaste was the clear winner, removing about 98% of bacteria from both new and worn surfaces. Denture-cleaning tablets performed comparably, clearing more than 97%. The two mouthwashes landed in the middle at roughly 86 to 88%. Cold and warm water rinses brought up the rear at 60% and 70%, respectively.

Microscope images backed up the numbers. After brushing, surfaces appeared nearly clean. After water rinsing, sizable bacterial populations remained, especially tucked into the grooves and pits of roughened material, exactly the kind of surface a well-used mouthguard presents.

Statistical analysis confirmed that the cleaning method mattered far more than whether the surface was new or old, which makes proper cleaning technique the single most controllable factor for parents and young athletes.

What Sports Families Should Know About Mouthguard Bacteria

A quick rinse under the faucet is not enough. A toothbrush’s scrubbing was the most effective approach tested, mechanically breaking up bacterial colonies and reaching into the grooves and scratches that build up on a mouthguard’s surface over time. Dissolvable denture-cleaning tablets came close, while the mouthwashes and plain water rinses left far more bacteria behind.

Researchers also noted that mouthguard replacement should factor in surface wear, not just whether a device looks obviously damaged. A mouthguard that still fits and appears intact may have developed microscopic roughness that makes it more hospitable to bacteria than when it was new. Parents should watch for visible signs of wear such as grooves, bite marks, or discoloration, and consider replacing heavily worn guards, though more research is needed to pin down specific timelines.

This was a small, preliminary study, just ten players from one team in one sport over a single season, and the laboratory methods captured only a fraction of the bacteria that might turn up on a real mouthguard. It measured contamination, how tightly bacteria clung, and how well different cleaning methods worked, but it never tracked whether any of the bacteria actually made the children sick. Larger studies across different sports, climates, and age groups will need to confirm the findings before they can be treated as firm guidelines. Still, the core message holds up: for the millions of kids who suit up for contact sports each season, the mouthguard is meant to be protective equipment. Without proper cleaning, meaning real brushing rather than just a splash of water, that same gear can become a reservoir for environmental bacteria, pressed right up against a child’s gums and teeth for hours each week.

Disclaimer: This article describes a small, preliminary study of ten under-12 football players from a single team over one season, combined with laboratory testing. It measured bacterial contamination, attachment, and cleaning efficacy, not actual infections or health outcomes, and culture-based methods detect only a fraction of the bacteria present. Larger, more diverse studies should confirm the findings before treating them as firm hygiene guidelines. It is not medical advice.