Health Benefits of Kissing

I happened to catch a Twitter post from "@MindblowingFact" that said "A kiss can be ten times more effective than morphine in reducing pain, as it's thought that it activates the body's natural pain-killers". Then I thought to myself; "is this why little kids always want someone to kiss their injuries to make them feel better? could this actually be effective?"

I found this article with some other health benefits:
1: Kissing helps prevent tooth decay
2: Kissing relieves stress
3: Exercising the muscles of the face can help keep you looking younger
4: Kissing burns calories
5: Kissing boosts your immunity
6: During a kiss natural antibiotics, and allergy antibodies are secreted in the saliva

It seems to be true, a report on the subject seems to confirm the 'mind blowing fact'. When someone is kissed endorphins are released which trigger parts of the brain that perceive pain. Much like an orgasm, a kiss can stimulate the release of these endorphins and create a sense of euphoria and pleasure, even when a person is in extreme pain.

All of these benefits are quite interesting to me and when reading, kissing is a bonding behaviour for most humans and even some animals. It was quite interesting to find that some populations find kissing actually revolting. The perception around exchanging saliva is considered grotesque. These populations found in South America, and the Himalayas are not convinced that there are many benefits to locking lips with their loved ones.

Do you consider any of these benefits when kissing? Or is kissing simple a natural expression of intimacy between yourself and someone you love? I admit that I had never thought of the benefits besides the sense of connection created.