11 fun facts about kissing

Kissing is not only a fun expression of love and affection - it also burns calories and strengthens the immune system. And remember - it is not allowed to kiss women in public on a Sunday in Michigan.

1. A normal kiss burns 6.4 calories per minute. A passionate kiss can burn up to 20 calories per minute. That's even more than swimming, which burns 12 calories in one minute, just like jumping rope.

2. Today, an average kiss lasts more than 12 seconds. In the 1980s, couples came up for air sooner than that: back then an average kiss lasted a mere 5.5 seconds.

3. Public kissing isn't always allowed everywhere. It's forbidden to kiss women in public on a Sunday in Michigan and Connecticut - these US states take the Day of the Lord quite seriously. In the subway in Turkey's capital Ankara, passengers are expected to adhere to "moral rules." A kissing Turkish couple spied on by security cameras was officially warned.

4. With an average of four kisses per person and day, Germany ranks second behind Sweden on the list of countries that are stingy kissers. People in France and Italy do much better: they kiss an average of seven times per day.

5. Researchers study kissing in a field of science called philematology. They've discovered two out of three people tilt their heads to the right when kissing.

6. Doctors are totally enthusiastic about kissing because it strengthens our immune system and slows down the ageing process. Just thinking about a kiss increases the flow of saliva, which in turn loosens plaque.

7. Smooching is great for road safety, too. Researchers found that people who hit the road freshly kissed are much less aggressive. They say that results in fewer accidents. But kissing while driving is not a good idea - please keep an eye on traffic!

8. People kiss in 90 percent of the countries worldwide. How and why differs from one country to the next. Three cheek kisses are a standard welcome in France, while in Japan, people only kiss if both parties want sex.

9. As affectionate gestures go, kissing is not just a social behavior we've developed over the centuries - it's an instinct we can observe in orangutans and other primates as well. Geese express affection by touching beaks, and elephants put their trunks into each others' mouths.

10. Kissing stimulates more than 100 billion nerve cells, while happiness hormones and adrenaline course through our bodies, letting our hearts beat faster. Blood pressure and body temperature rise, too.

11. A great deal of swapping goes on in a kiss: 60 milligrams of water, 0.5 milligrams of protein, 0.15 milligrams of gland secretion, 0.4 milligrams of salt and up to 22,000 bacteria.