How Gross Is it to Share Your Toothbrush?

Ah, friends. They're like family but cooler. Fully customizable. Fall and one of them will be right there to pick you back up. But as great as friends can be, they also do a lot of really stupid stuff. Stuff that blows your mind. Like, sometimes it seems crazy that you even hang out with people who make such crappy decisions. Stuff that, were it to get out, would be mortifying for anyone with even a shred of self-respect. Lucky for your friends, they've got you to ask their deepest, darkest questions for them. And lucky for you, we started this column to answer those most embarrassing of queries. Couples share stuff. Tacos. A credit card. A fork. A bed. Bodily fluids. But letting your partner borrow your toothbrush? The jury's out. A quick straw poll of friends elicited the following responses: "Ew," "Hell no!" "It depends what she's eaten," and, um, "Are we not supposed to do that?"

The scenario: Your friend's significant other is spending the night, and he's arrived empty-handed. No tacos or toothbrush. She searched the bathroom cabinet for a spare, but crickets. Not even one of those tiny travel toothbrushes that sometimes get handed out on international flights is gathering dust on the top shelf. What does she do? Declare "sharing is caring!" and hand over her own toothbrush? Or insist he goes to bed with fuzzy teeth and just prepare for a wake-up call of seriously nasty morning breath?

The facts: Hundreds of strains of bacteria live in our mouths (no matter how vigilant we are about our oral health), and they can set up home on our toothbrushes. A review of case studies published in Nursing Study and Practice in 2012 found that a toothbrush can be a breeding ground for disease-causing bacteria and viruses (as well as blood, saliva, oral debris and toothpaste).

The official line: The Centers for Disease Control and Prevention (CDC) doesn't recommend sharing a toothbrush because it transmits bacteria from one mouth to another, leaving brushers susceptible to all kinds of oral and general health problems.

But we kiss our partners, right? So can swapping saliva via a toothbrush really be that gross?

Couples can spread bacteria through kissing, sharing food and drinks and even holding hands, but sharing a toothbrush may be more risky, says Kenneth Magid, dentist at Advanced Dentistry of Westchester in Harrison, New York. "There may be a higher concentration of certain bacteria on a toothbrush, since the toothbrush's job is to actually break up the bacteria-containing build-up."

The worst that could happen: "Some individuals suffer oral conditions that simply are not worthy of sharing," says Gary Glassman, a Toronto-based dentist who travels the world to speak on the importance of maintaining great oral health. Want specifics? Try staph, E. coli and Pseudomonas for starters. Then there's beta-hemolytic streptococcus ("strep"), a bacteria that causes strep throat, resulting in sickness, a sore throat, fever, cough, swollen lymph nodes and difficulty in swallowing. "Mutant strains of strep cause dental cavities," warns Glassman.

If your gums bleed when you brush, you run the risk of bacteria entering your bloodstream, theoretically exposing you to communicable diseases like hepatitis B and HIV, says South Florida periodontist David Genet. Meaning couples who share a toothbrush could actually be sharing blood, not just saliva.

What will probably happen: Um, nothing. While no dentist is going to recommend sharing a toothbrush, the CDC admits to being "unaware of any adverse health effects directly related to toothbrush use." UK periodontist Eugene Gamble confirms that "the chances of transmitting disease-causing bacteria that wouldn't already be in the mouth are remote." If neither of you have an infectious disease or a compromised immune system, occasional toothbrushing-sharing is unlikely to do any harm. Genet agrees that "the danger factor is minimal since the body has an excellent immune system," adding that, "If it's a choice of brushing or not brushing our teeth, share as long as you know the owner of the toothbrush."

What toothbrush sharers need to know: For those who are determined to share a toothbrush, whether out of laziness, convenience or because you simply feel closer to your significant other when you have their bacteria swilling around your teeth and gums twice a day, at least keep it clean. Sorry, but a quick rinse won't suffice. "Toothbrushes are rarely cleaned thoroughly, and are often kept in warm, moist bathrooms, an environment ideal for bacterial growth," warns Glassman. After every use, rinse your toothbrush thoroughly to ensure the removal of all debris, allow it to air-dry, and store it in an upright position. If multiple brushes are stored in the same holder, don't allow them to touch each other. If either of you is sick or has a cold sore, stick to separate brushes.

Whether you share a toothbrush or not, don't forget the basic rules of oral hygiene. "Change your toothbrush every three months, after being sick, and if the bristles start to look worn," says Magid. "Remember to floss daily and when food is caught. You can even take the floss in the shower with you to make it part of your routine."

Whether you share that strip of floss or not is, of course, up to you.