Cavities Are Contagious Sharing bacteria can spread tooth decay By Matt Cantor, Newser User Posted Apr 2, 2011 2:53 PM CDT 4 comments Comments Cavities can be contagious. (Shutterstock) (Newser) – Candy and cookies aren’t the only cavity culprits: tooth decay can actually be contagious, scientists have found. That’s because cavities result from bacteria hanging around in your mouth—and these germs can be passed from person to person, the New York Times reports. It’s a noted problem in young children; they can pick up cavities when, for example, their mothers taste their food to check if it’s cooled. It’s also an issue among couples. “In one instance, a patient in her 40s who had never had a cavity suddenly developed two cavities and was starting to get some gum disease,” a dentist tells the Times. Turns out she’d just started dating a guy who hadn’t visited the dentist in 18 years. The best way to avoid a similar fate, the dentist says, is to floss and brush often, and try chewing sugar free gum: it stimulates saliva, which can rinse away the germs.