 to stop brushing your teeth in the shower. Using the water from your shower head could put you at risk of biofilms and bacteria that can cause lung infections if inhaled or swallowed. And chances are you're placing your toothbrush on a surface in there which can spread bacteria, mold, or fungus to your mouth the next time you use it. This is even worse if you share a shower with other people. The moisture and heat also makes the perfect environment for bacteria to grow on your toothbrush in between brushes, so if you really want to keep doing it, at least take your toothbrush out to dry completely in between.