5 Habits That Promote Bacterial Growth on Your Toothbrush

1. Sharing Toothbrushes
   Even if a personal toothbrush harbors bacteria, they primarily originate from your own mouth and usually don't cause illness as long as your immune system is healthy. However, sharing toothbrushes increases the risk of cross-infection.
2. Storing Toothbrushes Together
   When bristles touch, bacteria can transfer between toothbrushes. It’s recommended that everyone uses a separate toothbrush holder or cup.
3. Keeping Your Toothbrush in the Bathroom
   In most households, the bathroom combines as a toilet, shower, and sink area. In this case, it’s best to store toothbrushes and cups in a cabinet or another room to avoid contamination from airborne bacteria released during flushing.
4. Neglecting to Clean the Toothbrush Holder
   Even toothbrush holders can accumulate dust and grime, creating a breeding ground for bacteria. This can lead to bacterial overgrowth on your toothbrush. Clean the holder at least once a week.
5. Storing Toothbrushes with Bristles Down
   After use, toothbrushes should be stored upright in a cool, ventilated area to air dry. Storing them bristles-down in a damp environment promotes bacterial growth. When traveling, ensure the toothbrush is dry before placing it in a travel case.

Resources：https://zhuanlan.zhihu.com/p/412279529