There may be a genetic component to obsessive licking, as with other obsessive behaviors. There are lots of things that can cause it, sometimes even medical reasons, such as liver disease, kidney failure, Cushings disease. (I think) Stress or boredom can cause it. It can be an appeasment thing. My smallest Chihuahua is fairly submissive, I think, just on account of her size. Stress is another thing I suspect could cause this re-directive type behavior. It's like an outlet maybe. Sometimes they just like the taste of salty skin. And in the case of some lickers, like how Dan so colorfully describes Daisy, which also describes Toker, I almost think they're being humorous/playful or affectionate at those kinds of times. But Chulita will lick other things too..the floor, the couch. It's not constant, but she does it a fair amount. It's something where any kind of correction, like, "no," haha....just makes them lick more. If scolded, they just appease you more and that means, lick more. So, I tried using the "enough" which was trained in other contexts, but using positive reinforcement methods, so when they hear that word, it doesn't mean something bad, like, "No!" It has instead, a history of being paired with treats. It means stop what you're doing. And then I need to distract them to do something else.