When you're talking to someone whose every syllable is accompanied by an unwelcome saliva shower it's sometimes hard to hear what they're saying over the deafening germophobic thoughts running through your head. How justified are you in freaking out over a stray spray of spittle? We investigated.
"Eighty percent of all infections are transmitted by direct and indirect contact," explains Philip M. Tierno, Jr., a professor of microbiology and pathology at the NYU School of Medicine. Direct contact is coughing, sneezing, or kissing. Indirect contact is—for example—when a sick person coughs into their hand, touches a doorknob, and then you touch said doorknob. Then you go on to touch what Tierno calls the "conduits of entry into your body"—your eyes, nose, mouth, or a break in your skin. That's when infection ensues. (The other 20 percent of infections stem from insects and arachnids, like ticks and mosquitos, that impart germs by biting you; contaminated food or water; and airborne particles that you inhale.)
But let's get back to the spit—that's a direct hit. "Talking can spew out aerosol particles very easily," Tierno says. The rhinovirus (which causes the common cold), and norovirus (the stomach flu) can both be present in someone's spit. Cold and flu viruses—because they grow in the lungs and nose — are the most likely ones to spread via a little burst of saliva, says Charles Gerba, a professor of microbiology and environmental sciences at The University of Arizona's Mel & Enid Zuckerman College of Public Health. And only extremely small doses of the norovirus need to be transferred in order to cause infection.
Theoretically, one or a few particles is enough to create a problem, Tierno says—but not necessarily reason to panic. (More on this in a second.) Also: If your face is sunburned or if you have open wounds and the person who spits on you has something like strep throat, there's a chance you could wind up with a pimple, a skin infection, or—in very rare cases—a flesh-eating situation, Tierno says, since your skin is irritated and might be cracked, and therefore more vulnerable to infection.
Of course, to actually get sick from spit, a whole series of events have to unfold. First: The person doing the spitting has to be sick—infected with one of the above viruses or bacterium. (You don't really have to worry about herpes, or viruses like Epstein-Barr, which causes mono—those mostly transfer via kissing or sharing drinks, not via a drop of saliva on your face, Gerba says.)
Second: "To become infected you would have to get the virus on your hands and then bring your hands to your nose or eyes," Gerba says. Unless the spit lands directly in your mouth or nose—in which case, your odds of infection are slightly higher, he says. Otherwise, "a drop of saliva on your face is unlikely to result in transmission."
Regardless, if you want to be extra cautious, when you feel a wet glob land on your face, wipe it off and wash your hands, or use a hand sanitizer with at least 60 percent alcohol—an amount research shows is more effective at killing germs. If you're able to step away, best to dab the hand sanitizer direct on the spot of impact and then wipe to kill it.