Most athletes, and parents of young competitors, know a mouth guard can be essential in preventing injuries while they play. What they may not know is that the same piece of equipment that offers protection can also lead to life threatening illnesses.

"He used to wear it where they were attached to the cage. We never took it off, and then he'd put it in his mouth. I mean, we never cleaned it. NEVER," said Patricia Howell, the mother of an athlete.

But the results of a new study from Oklahoma State University may have athletes rethinking those actions. After swabbing dozens of mouth guards, researchers found that germs keep on  multiplying dramatically.

"The mouth guard becomes highly, highly contaminated. In other words, every time the athlete puts the mouth guard into his mouth, it's like putting a handful of dirt in his mouth," said Dr. Tom Glass, a microbiologist.

Mouth guards look solid, but are actually porous. That makes them flexible, but also encourages bacterial growth, from staph to strep to pneumococci.

"Not only are we worried about the effect right there in the mouth, we're worried about the effect in the lungs, with exercise-induced asthma from molds, and we're worried about the bacteria in the stomach that will produce toxins that will cause nausea, vomiting and diarrhea," said Dr. Glass.