body + soul reports on this finding:

“Rhett Butler famously told Scarlett O’Hara in Gone with the Wind: “You should be kissed and often. And by somebody who knows how.” There are few of us who don’t dream of swooning in someone’s arms, Hollywood style, in a lingering meeting of lips.

It’s no surprise most people find kissing pleasurable, since there is a larger area of the brain devoted to sensations from the lips than from the entire torso. Not only that, but five of our 12 cranial nerves are activated during kissing.

“Kissing is an enormous stimulant to certain brain systems. A huge amount of biological information appears to be sent to your brain during a kiss. This may be why a kiss with a stranger immediately turns you on or off,” says Dr Helen Fisher, a professor of anthropology at Rutgers University in the US and author of Anatomy Of Love (Random House).

“Kissing may be an evolutionary mechanism. It seems women are more attracted to men who have opposing immune systems, which would provide the best protection for offspring.”

In good news for Valentine’s Day lovers, activating certain nerve endings through kissing also signals our brain to produce oxytocin, a hormone that promotes calmness and wellbeing.

Increased levels of oxytocin are also produced by massages, suggesting that kissing could also be a natural de-stressor.

But Dr Fisher warns kissing depends on context. Kissing someone for the first time is more likely to result in a rush of dopamine and norepinephrine, two natural stimulants produced by the body when it encounters new experiences.

“Mad love-affair kissing might be just the opposite of relaxing,” she adds.

Bonding process Oxytocin is sometimes called the “bonding hormone” or the “love hormone” because it appears to encourage bonding in animals. In a famous US laboratory study on voles, oxytocin levels were shown to be an important factor in whether these small rodents created important male-female bonds.

North American prairie voles produce large amounts of oxytocin and are the only species of vole that mate for life. Mountain voles, which produce virtually no oxytocin, are loners who have multiple mates.

How this study relates to humans is still not clear. Professor Wendy Hill studied kissing couples at Lafayette College in Pennsylvania, US, and measured the levels of oxytocin in their saliva and blood. To her surprise, only the men showed an increase in oxytocin after kissing. In the women, the oxytocin levels actually declined.

Professor Hill also measured cortisol, a hormone related to stress. “After kissing, both men and women showed lower cortisol levels, suggesting kissing does have a calming effect,” she says.