FAQs on their purpose and problems, and some practical advice
What are dog greetings?
Greetings between dogs allow people to assess their own ability to handle stress, but that is of course not their primary purpose. Greetings serve a lot of functions in social species, from reducing uncertainty, fear and arousal to gathering information. They can be used to signal status and to increase tolerance for being in close proximity to one another, and may also be important in conflict resolution and reconciliation. Dogs, as we know, are intensely social creatures, and while it’s not possible to say what canine greetings are actually for—they have not been studied enough —it’s likely that they serve more than a single purpose.
via Whisker Therapy