When they are young, dogs constantly lick their mothers’ faces. It is believed that they do this to see whether she has food for them, presumably from a hunt.
Humans Taste Salty
The rather unromantic part of why dogs lick you is that you taste good. Humans are naturally salty to the tastebuds, and dogs’ heightened sense of taste seems to enjoy this.
Dogs Say Hello This Way
Aside from seeing you, they feel more comfortable the more senses they can engage. So smelling you and tasting you are all part of a greeting ritual that sets them at ease.
Dogs are Offering You a Refresher Lick
In part, this may have been to show respect and obedience to pack leaders. In that way, it is showing you that you are the alpha.
What Dogs Find Out By Licking
When a dog licks your hand and smells it, he can run a background check on you, so to speak.