Is It Really That Bad to Share a Toothbrush?

You have an impromptu sleepover with a date or forget to pack your toothbrush on a last-minute weekend getaway, and are now left wondering whether to borrow a toothbrush. But as harmless as sharing a toothbrush may sound, it comes with a lot of unnecessary health risks.

The mouth is home to more than 700 types of bacteria, according to a study in the Journal of Clinical Microbiology. Bacteria that can be effortlessly shared via kissing, drinking out of the same cup, and yes, using someone else’s toothbrush—because you’re technically swapping bodily fluids aka saliva. While not all 700 of these bacteria are harmful, some like staph and E. coli, can lead to infection and illness.

“Just think of how easy it is to spread cold virus,” says Steven F. Schwartz, DDS, a New York City-based dentist. “A toothbrush would be a good vector for spreading bacteria and viruses.”

The common cold and strep throat are easily spreadable, especially among children, and are probably the more likely outcomes of sharing a toothbrush, but severe illnesses and diseases like herpes, pneumonia, and even HIV and HPV, can also be transmitted via toothbrush swapping. Sharing a toothbrush means that whatever was in your friend’s mouth is now in your mouth. And if the person whose toothbrush you borrowed doesn’t rinse and clean it properly, it’s likely that day-old food particles stuck on the brush will end up stuck in your mouth, which is admittedly not dangerous, but really gross if you think about it. (Here are 11 more do’s and don’ts your dentist wants you to know.)

So if you ever happen to be stranded in the middle of nowhere without a toothbrush and no drugstore in sight, Dr. Schwartz says using your finger or a washcloth is a better alternative than grabbing a friend’s toothbrush.

Besides making sure you’re the only person using your toothbrush, you should also make sure you’re cleaning it properly. Both Dr. Schwartz and the American Dental Association recommend rinsing your toothbrush with water after every use and storing in an upright position, separate from other toothbrushes, because you don’t want them accidentally touching. “As for sanitation, at least rinse with warm water and allow it to dry,” says Dr. Schwartz. “There are also UV sanitizers on the market.”

Another DIY sanitizing technique is to rinse your toothbrush with Listerine, baking soda, and/or alcohol for an extra deep cleaning every couple of days. The ADA also advises replacing your toothbrush at least every 2 to 3 months, and always immediately after illnesses like the flu or cold. (Next, check out what happens when you don’t replace your toothbrush often enough.)