Can too much kissing damage your lips?

couple kissing
Ewww! Don't they know that kissing can transfer 250 colonies of bacteria from one person to another?

When -- and more importantly, why -- did we decide that kissing was so great? Perhaps it's a relic of the innate reflex to suckle the breast (no, really). Or perhaps it's a learned behavior, one that possibly evolved from our ancient ancestors desire to identify the health and wellness of a potential mate through examination of the saliva [source: NPR]. Whether the behavior is innate or learned, it's not practiced across all cultures. While most of us kiss, nearly 10 percent of cultures around the world refrain from kissing, usually for reasons of cleanliness.

People have developed a particularly pleasant physical reaction to kissing and being kissed. The chemical oxytocin, which has been shown to bond humans to one another, is produced in the brain during a kiss. At this point, the reward center of the limbic system switches on and releases the chemical dopamine, which leads to the pleasurable feelings we experience during kissing. In other words, we get the same reaction from kissing that we do from chocolate and cocaine [source: Ahlstrom].


Kissing serves as an obvious emotional cue; it conveys affection, attraction and love. As thrilling as it is, however, it can also be dangerous (not to rain on anyone's parade or anything). The herpes simplex virus 1 (HSV1), which causes cold sores, can be transmitted from one person to another during a kiss. The same goes for syphilis. In fact, kissing is considered one way to transmit some sexually transmitted diseases. Of course, there's mononucleosis and glandular fever (the so-called kissing diseases), as well as colds, the flu and myriad other diseases that can also be transferred from a sick to a healthy person through kissing.

None of this should come as much of a surprise (at least not to the 10 percent of cultures that abstain from kissing). The average open-mouthed kiss can transfer around 250 colonies of bacteria [source: Harrison]. The mouth contains bacteria and saliva -- which, while relatively harmless, can actually hurt the thin skin of your lips. Find out on the next page how kissing can not only transmit disease, it can actually damage your lips.


How Kissing Could Damage Your Lips

lucha libre kissing
Even lucha libre masks won't prevent saliva from reaching the lips and damaging the tender skin there.

The skin on your lips is fairly unique. The rest of the skin across your body has about 16 layers. The outer layer is called the stratum corneum. It's a barrier that protects the other layers beneath made up of dead skin cells that have dried and hardened, or cornified. These cornified skin cells (called corneocytes) are eventually sloughed off and are replaced by newly dead cells from the layer beneath. If you're an average person, you shed about nine pounds (four kilograms) of dead skin cells each year [source: Reucroft, Swain].

On the other hand, your lips are thinner, with about three to five layers. In fact, the skin on your lips is so thin that it gets its color from the blood-filled capillaries in the mucous membrane beneath. This means that the skin on the lips has less protection from damage, and the lips also have the additional misfortune of being located around the mouth. Within the mouth, as we know, saliva is produced and saliva is laden with digestive enzymes designed to jumpstart the food digestion process. A pair of these enzymes, amylase and maltase, can deteriorate the thin skin of the lips every time we lick them with our tongues [source: Gardner].


Saliva is also introduced to the lips during kissing. We often prepare for a kiss by wetting our lips with our tongues. Even a brief peck moves saliva from within the mouth to the outer lips. And saliva is transferred more abundantly during what philematologists (scientists who study kissing) call passionate or open-mouthed kissing. Not only is the individual's own saliva smeared across his own lips, saliva is transferred from person to person. All of this can lead to damage to the thin skin of the lips from kissing.

While saliva can damage the lips, it also plays an important role in kissing. It contains several hormones that are transferred from kisser to kisser, one of which is testosterone. This hormone has been shown to increase sexual desire and physical sensitivity in both men and women [source: Blackwell Publishing]. If kissing can damage the lips, perhaps it's worth the risk.


Lots More Information

Related HowStuffWorks Articles


  • Ahlstrom, Dick. "Sexual chemistry - scientists get to grips with kissing." Irish Times. February 14, 2009.
  • Blackwell Publishing. "Testosterone patch benefits women with low sexual desire." August 15, 2007.
  • Gardner, Amanda. "Dry lips won't take a licking." HealthDayNews. December 27, 2003.
  • Hanson, Lane. "The (mostly) blissful history of 'kissing.'" NPR. February 11, 2007.
  • Harrison, Erica. "Science of smooching." Cosmos. June 2007.
  • Lip Augmentation. "Lip anatomy." Accessed September 10, 2009.
  • Reucroft, Stephen and Swain, John. "Does the dust in my house really include my own skin?" Boston Globe. September 1, 2008.