Alain Bashung sang it with elegance in one of his latest songs: “The kisses received, did you know they last? By biting the lip, the taste returns.” Tender, passionate or comforting, kisses embody affection and love. But why does a kiss on the mouth hold such a special place in our relationships?
Why do we kiss on the mouth?
In the eyes of others, before becoming a body or a personality, we are first a face. It concentrates a large part of our identity and expression. A smile, a gaze or a movement of the lips can sometimes translate an emotion.
A kiss brings this deeply intimate part of two people closer together. It reduces distance, engages several senses, and implies mutual trust. It can express desire, love, tenderness, or simply the wish to reconnect.
Its exact origin remains shrouded in mystery. Several hypotheses have been proposed. The kiss could, in particular, allow an unconscious evaluation of a partner through scent, taste, and proximity. It could also strengthen bonds that are already established.
These avenues are nevertheless difficult to prove. The kiss is at once a bodily, emotional, and cultural behavior, whose meaning varies from one person to another and from one society to another.
The romantic kiss is thousands of years old
The romantic kiss is not a modern invention. Texts from Mesopotamia and ancient Egypt mention lovers’ or sexual kisses as early as the third millennium BCE.
These accounts show that the practice existed in several ancient regions. It is therefore hard to attribute a single birthplace before it gradually spread around the world.
However, not everyone kisses on the mouth. An anthropological study conducted across 168 cultures identified romantic or sexual kissing in fewer than half of them. In some societies, intimacy is more expressed through touch, close face-to-face contact, caresses, or other codified gestures.
The French “bise” also has its rules. Its number, the side to start on, and the circumstances in which it is practiced differ from region to region.
Did you know? The “Eskimo kiss” isn’t really a kiss
In Western culture, it involves rubbing noses with another person. The Inuit gesture, called kunik, is different: the nose and upper lip rest on a cheek or the forehead to inhale the person’s scent. It expresses mainly familial affection and isn’t necessarily romantic.
What happens in the body during a kiss?
The lips are especially sensitive. When they come into contact, many receptors send information to the brain. Touch then blends with taste, smell, skin temperature, and the emotions felt.
The brain activates circuits of pleasure and attachment
A desired kiss can stimulate mechanisms associated with reward, pleasure, and emotional bonding. Dopamine and oxytocin participate in these processes, but calling them simply “happiness hormones” would be reductive.
The context matters a lot. A first kiss that’s been anticipated for a long time does not trigger the same reaction as a casual or unwanted kiss.
Heart rate and breathing can also quicken. Attention focuses on the partner, while the surrounding environment seems to fade away for a moment. This sensory experience partly explains why a kiss can leave such a clear memory.
A private language that relies on consent
The kiss can strengthen complicity, reassure, or express what words sometimes struggle to convey. It is not, however, an obligation within a relationship, nor a universal proof of love.
Some people enjoy it a lot, while others are less comfortable with the gesture. Desire and consent must stay mutual. A kiss only produces its pleasant effects when it is truly shared.
How many microbes do we exchange when we kiss?
Kissing isn’t just about sharing emotions. When a French kiss happens, partners also share saliva and the microorganisms it contains.
A small study of 21 couples estimated that a ten-second intimate kiss could transfer about 80 million bacteria. This striking figure should be interpreted cautiously. It comes from a limited sample.
Researchers also observed that partners had more similar oral microbiomes than people without an intimate relationship. Kisses can contribute to this similarity, but they aren’t the sole cause. Shared living, diet, environment, and hygiene habits also play a role.
Contrary to a common belief, there is no evidence that kissing harmonizes the immune systems of partners. The hypothesis that these exchanges prepare the female body for a future pregnancy has not been sufficiently demonstrated.
Can you get sick from a kiss?
Most bacteria exchanged are harmless for healthy individuals. However, some infections can be transmitted by saliva or very close contact.
This includes the Epstein-Barr virus, responsible for infectious mononucleosis. Respiratory viruses and oral herpes can also take advantage of this proximity.
So it’s best to postpone kissing when you have a fever, infectious symptoms, or an active cold sore. This precaution is particularly important when a partner is frail or immunocompromised.
Good practice
Good oral hygiene helps limit bacteria responsible for cavities and gum disease. It doesn’t require disinfecting your mouth before every kiss!
Do animals kiss too?
Some animal behaviors resemble our kisses quite a bit. Chimpanzees and bonobos can bring their lips close together during social, sexual, or reconciliation interactions.
Birds sometimes touch beaks. This gesture can participate in courtship, maintaining the bond, or transferring food. Parrots also engage in mutual grooming.
Dogs lick faces, while cats rub, groom, or cuddle against each other. Horses may nuzzle softly as part of reciprocal grooming.
However, avoid automatically ascribing human intentions to them. A touch between two mouths, two muzzles, or two beaks is not necessarily a romantic kiss. It can serve to feed, soothe, communicate, or establish a social bond.
The kiss, a small gesture that can say a lot
The kiss is therefore neither universal nor biologically indispensable. Its power largely comes from the meaning two people choose to assign to it.
It costs nothing, creates no waste, and can offer a moment of closeness in days that move too fast. As long as it is desired by both parties, it is perhaps one of the simplest gestures to nurture tenderness.
