Anna:

Actually, saliva has antibacterial properties. So it was a clever impulse, if somewhat gross from an adult point of view. ;-)

Mike Sakasegawa:

As far as I know, you are more likely to introduce bacteria into a wound by licking it than killing any that are already present, even with the antibacterial properties of saliva. This is what I've always been told in first aid classes, and I've also heard (though I haven't researched it very well) that bites from humans are more prone to infection than bites from most other animals, due to the bacteria that live in human mouths.

Jonathon:

Indeed. I remember this awesome line from my health and physical education general ed class: "A simple human bite, if left untreated, can rapidly develop into a life-threatening infection."

Anna:

But a human bite involves teeth, which are indeed filthy. I heard saliva had a big part in cleaning teeth, so much than dentists say someone who salivates enough or a lot has a lot less chances to have cavities than someone who doesn't.
Could be that it's not verified, though.

Mike Sakasegawa:

My dentist has told me that the part of the teeth that tend to have the most plaque is the inside part of your lower middle incisors, and that the reason is because it's right next to the salivary gland.

Mike Sakasegawa:

In any case, a quick Google search of "wound licking" seems to show that some scientists and doctors think that it could help healing, but most say that the risk of infection outweighs the potential benefit. And we all know that the Internet is never wrong.