The study, published in General Dentistry, found mouthguards can be reservoirs for large numbers of bacteria, yeasts and molds that can possibly lead to life and/or health-threatening infectious/inflammatory diseases.

Lead author Thomas Glass said that athlete mouthguards appear solid, but they are very porous, like a sponge, and with use, microorganisms invade these porosities.

"Everything that a microorganism needs to survive, including food and water, can be found in a mouthguard," Glass said in a statement.

However, athletes often chew on the mouthguard and some throw it in with dirty, sweaty gear. Some never clean the mouthguard, Glass said.

To prevent illness caused by a mouthguard Glass advises to:

-- Brush teeth before wearing a mouthguard.

-- Never share a mouthguard with teammates.

-- During sporting events, have a backup mouthguard.

-- Purchase disposable mouthguards.

-- Clean mouthguards before storing them.