12 surprising facts about kissing

Kissing isn’t just about fun and love. Along with a smattering of germs, a smooch can provide bona fide health benefits.
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A kiss isn’t just a kiss. And it’s not just a sign of affection, either. According to research it’s an assessment tool for women, a persuasion tool for men and a relationship sealer for couples. But it’s also a way to de-stress, strengthen your immune system and stoke lusty desires. But it can be addictive and can also cause cavities. Here, 12 surprising facts about kissing.

-- By Martica Heaner Ph.D

1 of 14 A couple kissing (Guido Mieth/Getty Images)

Kissing Fido might transfer dental bacteria

Everyone knows that a dog’s mouth is a minefield of muck. But when you’re being slobbered with love, your sweetie’s sloppy tongue may be hard to resist. However, you might want to keep your mouth shut: A 2012 study in the Archives of Oral Biology found that people and dogs can transfer bacteria that cause gum disease.

Researchers in Japan collected specimens of dental plaque from 81 men and women and their 66 pet dogs – poodles, Chihuahuas, Pomeranians, Labs, Jack Russells and other breeds. The numbers and types of mouth bacteria were analyzed and correlated with the amount of contact the owners said they had with their dogs. Canine and human mouths had varying bacterial profiles, but one type of bacteria common in dogs but not humans was found in 13 people whose dogs also had it, although two of them reported having little contact with their dogs. The study did not determine whether these bacteria were linked to more cavities, but their plaque potential suggests that it’s a good idea to brush your teeth after a snuggle session with Fido.

2 of 14 A woman cuddling with a dog (Winnie Au/Getty Images)

A mother’s kiss may cause cavities

Kissing humans may be just as risky as kissing pets, especially when it comes to moms and their children: There’s a fair amount of saliva-sharing when kissing babies, and multiple studies have found a link between the presence of the cavity-causing bacteria mutans streptococci in moms and their kids. Preschool kids with high levels of these bacteria have a higher prevalence of cavities.

A review of the 46 studies in the journal Pediatric Dentistry found that mothers’ saliva is a primary source of transmission of this bacteria in children, especially in moms with high levels of this bacteria. Kids who breast-fed also had a greater likelihood of transmission. Several studies showed that interventions to clean out mom’s mouth sometimes helped decreased the presence of the bacteria, or the number of cavities, in kids. Take-home message: Avoid sharing eating utensils, brush before you smooch and minimize wet kisses.

3 of 14 A mother kissing her baby (Klaus Vedfelt/Getty Images)

But mommy’s kiss also helps baby grow

Of course, babies who are smothered with love are healthier and happier than babies who experience minimal physical contact. “Kissing a baby, and all the affection that goes with it, helps a baby grow,” says Tiffany Field, Ph.D., the director of the Touch Research Institute at the University of Miami Medical School. Field’s research has shown that the more grooming and physical contact a baby receives from the mother, the greater the growth of the child. Touching stimulates pressure receptors all over the body, and the body reacts to that stimulus. “Babies who get extra touch and stimulation thrive,” Field says.

4 of 14 A healthy, happy baby (Katarina Premfors/Getty Images)

Kissing can boost your immune system

OK, so mouths are filled with germs. But what doesn’t kill you – or give you cavities – makes you stronger. A 2003 study in Physiology & Behavior found that kissing can improve resistance to allergic triggers.

Researchers studied 60 people with skin or nasal allergies – allergic rhinitis and atopic dermatitis. An additional 30 subjects without allergies were a control group. All spent 30 minutes in a private room kissing their spouse or partner while listening to romantic music. In a follow-up experiment, the same subjects embraced their partners for 30 minutes, but without kissing.

Before and after each cuddle session, participants were given skin-prick tests to gauge inflammatory reactions to a variety of allergic triggers. The nonallergic subjects experienced no changes from kissing. The allergic subjects showed no decreased allergic response from hugging alone. But kissing reduced some nasal and skin reactions, causing the researchers to conclude: “The direct action of love may be beneficial, which may in turn reduce allergic responses.”

5 of 14 A woman blowing her nose (Picture Press/Getty Images)

Making out might make up for a missed yoga class

Kissing may not make you flexible, but it may produce the same reported relaxation effects as yoga or meditation. A 2009 study at Arizona State University  asked 52 adults to spend the following six weeks making kissing a priority in their lives by increasing the amount of time and frequency spent smooching their spouse or live-in partner. Reminder emails were sent throughout the study to prompt participants to amp up the volume of their affections.

After the lip-smacking intervention, compared with a nonkissing control group, the kissers showed significant decreases in levels of stress as measured by a validated psychological stress scale. Not surprisingly, the kissers also showed improvements in their levels of relationship satisfaction with their significant others.

6 of 14 Person doing yoga (Goldmund Lukic/Getty Images)

Most people are right-headed kissers

Smooth smooching requires that heads tilt just so to allow ample space for locking lips without noses clashing. And humans may be hardwired to lean in a way that facilitates this smooth union. Irish researchers found that 80 percent of kissing couples turned to the right. In a 2006 study, they also found that around 77 percent also turned right when kissing a doll.

A 2011 study in the psychological journal Laterality had 57 men and women plant 35 kisses on a life-sized doll as its head was randomly rotated to face head-on or at different right/left angles. More than 70 percent of subjects turned right and were more rigid in sticking to that side, no matter what direction the doll was turned. Left-turners were more flexible in adjusting to the doll’s position. Interestingly, kissing position preferences did not seem to be related to handedness; equal numbers of right and left kissers were right- and left-handed.

7 of 14 People kissing with tilted heads (Chris Fortuna/Getty Images)

Kissing can seal the deal – or call it off

Be forewarned: A first kiss can very well be a last. Psychologist Gordon Gallup Jr., Ph.D., at the State University of New York in Albany, surveyed nearly 200 men and women. The majority reported having experienced that after the first kiss with someone they were initially attracted to, the chemistry wore off.

The women were pickier than the men, with 66 percent reporting that a first kiss could be a turn-off, compared with 59 percent of the men.

A 2007 study in the journal Evolutionary Psychology might explain why. Young women surveyed reported that good or bad teeth, breath, mouth taste and kissing skill all played a role in determining whether to kiss at all, or to continue kissing someone.

8 of 14 Man and woman looking unhappy (Cavan Images/Getty Images)

Kissing keeps men faithful

Although men were more likely to see kissing as a prelude to sex, according to a 2007 survey of young adults, they felt like a stronger bond was created from post-coital smooching if it was with a long-term partner, compared with a short-term one.

Feelings of connectedness are thought to intensify due to the stimulation of the hormone oxytocin. “This is the hormone of love, and the better the oxytocin levels, the more capacity for love,” explains psychotherapist Arthur Janov, Ph.D., author of “The Biology of Love” and the director of the Primal Center in Santa Monica, Calif. “We have found that those who cannot commit in a love relationship are low in oxytocin.”

9 of 14 Couple looking at each other (Gary John Norman/Getty Images)

Kissing mimics a love drug

The same brain areas linked to reward and addiction light up when couples link lips. Rutgers University researchers conducted brain scans of men and women while they looked at pictures of partners with whom they reported being deeply in love. The 2005 study in the Journal of Comparative Neurology  showed that when looking at their beloved, brain regions associated with the reward-seeking neurotransmitter, dopamine, showed elevated activity.

Lead investigator of the study, Helen Fisher PhD, an anthropologist at Rutgers University in New Jersey explained the findings at symposium on kissing held at a 2009 meeting at the American Association for the Advancement of Science: Kissing may have evolved as a way to stimulate brain systems associated with sex drive, romantic love and attachment so that humans are triggered to seek a variety of potential mates, then focus attention on one for mating, and finally be able to tolerate that mate long enough to raise a child as a team.

10 of 14 A brain scan (Thomas Tolstrup/Getty Images)