In the case of the French kiss, the tongue is also an important part. Lips have many nerve endings so they are sensitive to touch and bite.
Research indicates that contraction of HIV via kissing is extremely unlikely, although a woman has been infected with HIV by kissing in 1997; both the woman and infected man had gum disease (so transmission was through the man's blood, not saliva).
Blown kisses are also used when a person wishes to convey affection to a large crowd or audience. In written correspondence a kiss has been represented by the letter 'X' since at least 1763.
More liberal-minded societies, such as that of Lebanon or Egypt, allow such kisses as greetings; more secular-minded individuals living in more traditional societies may have a similar view. Kisses on the cheek are a very common form of greeting among members of the same sex in most Islamic countries, following the Mediterranean pattern.
Source: Wikipedia > Kiss
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