Just a Kiss? 4 Infections Transmitted Through Kissing

You may think a kiss is just a kiss, but in reality, it can be much more. Smooching can be romantic, but it can also transmit a variety of infections.

"When I think of the infectious risk of kissing, what comes to mind are viral infections," says Bruce Hirsch, MD, attending physician in infectious diseases at North Shore University Hospital in Manhasset, New York.

Believe it or not, bacterial infections are much less likely to be transmitted through kissing, Hirsch says. "You don't think of bacteria as a major problem," he says.

A variety of respiratory illnesses can be transmitted from one person to the another through kissing, says Jorge Parada, MD, an infectious disease expert at Loyola University Health System in Maywood, Illinois. "Any infectious disease that would be shed from the airways of the body could be transmitted in a kiss," he says.

Before you lock lips with someone, consider that the following all may be transmitted through kissing:

1. Herpes simplex virus type 1. This virus, spread not just through sharing kisses but sharing towels and eating utensils, is the culprit that causes cold sores. (These are quite different from canker sores, which are inside the mouth and aren't contagious.) Once you get herpes simplex, the virus remains dormant in the nerve cells and can be reactivated by everything from sun exposure to stress.

2. Infectious mononucleosis. Famously known as the kissing disease, this illness is caused by the Epstein-Barr virus. It's transmitted through saliva and is most common in 15 to 17-year-olds.

"What happens is that high concentrations of virus are shared in the saliva and oral secretions," Hirsch explains. Mono typically causes a sore throat, swollen glands, and fatigue that persists for several weeks.

3. Colds. Just as there are over 100 viruses that cause a cold, so there are myriad ways to catch a cold. If you're around a cold victim who talks, coughs or sneezes, you may be the next unlucky victim. Colds also are spread through hand to hand contact (like sharing utensils or towels), but you can also catch a cold through kissing, Hirsch says.

4. Flu. You can not only spread this virus to others who are up to six feet away, but you can get flu even by touching an object that has some virus on it - and then touching your mouth or nose. You can also get it from kissing someone with the flu, Parada says, and you may not even know the other person is sick. A person starts being contagious a day before  he develops symptoms, and continues to be contagious for up to a week after getting sick.

While it's sometimes apparent when someone has a contagious illness--there's a visible cold sore on their lip, or they're coughing and sneezing--it's not always easy to tell.

"A person has viral shedding even before they have any outward manifestation of a cold sore," Parada says. So you could kiss someone with perfectly normal looking lips and wind up with herpes simplex.

One thing you don't have to worry about catching from a kiss is gingivitis, or gum disease. "That has more to do with somebody's personal hygiene," Parada says. "It has more to do with the care that you take of your teeth."


"Cold sores: Causes." The Mayo Clinic.


"Common cold: causes. The Mayo Clinic."


"How Flu Spreads." National Institute of Allergy and Infectious Diseases. National Institutes of Health.