[evan_au (OP)]

When I come home, my dog always tries to lick my face, and seems to focus on licking my mouth. (Yuk!)

Why do they do this?
- Could it be a dog greeting: "Hi, what's for dinner tonight?".
- Could it be a danger to dogs: "Oh, chocolate! I think I'll eat a chocolate bar!" (dog gets very sick...)

[JP]

It is probably a social greeting signifying submission.  Basically a "Hi, master!  I'm happy to see you!"

Another option is that it's a sign of hunger, since puppies will lick their mother's face to get her to regurgitate food for them.  Licking the food-giver to indicate hunger holds over in adult dogs, apparently.

(I got a new puppy this year, so I read a couple of books on dog behavior and that's where I'm getting this info from: The Other End of the Leash by Patricia McConnell is a good resource).

It could be a danger if you make a habit of walking around with chocolate bar smeared on your face, but unless this is a problem for you, it's probably not an issue for your dog.  :p

[CliffordK]

Of course humans also have a tendency to give a loved one a kiss too. 

Personally I've never let lick my face, and I think they quickly learn the bounds put forward by their family, and perhaps the bounds put forward by each individual in the family.  You can say no, or otherwise redirect the behavior.

[evan_au (OP)]

Discussion relating to "Why is chocolate bad for dogs?" split off here.

[nicephotog]

and seems to focus on licking my mouth. (Yuk!)

evan_au: Why do they do this?
- Could it be a dog greeting: "Hi, what's for dinner tonight?".

jp: Another option is that it's a sign of hunger, since puppies will lick their mother's face to get her to regurgitate food for them.  Licking the food-giver to indicate hunger holds over in adult dogs, apparently.

I have a policy of raising a puppy with me(physically present always) , and in terms of sleeping, because of replacing the mother and various points relating the "presence" process of nurture in terms of bond,company - boredom, anti-neglect of the process and then finally synthesis of parent replacement, i have the animal in either a box with my hand dangling in it or sleep on the floor.
However, when lying on your back whether large or small creature, one thing that gets poked in your mouth when manipulating your mouth open is their nose! Sometimes, it then sits there the tip poked in your mouth!.
I cannot think of one i've had that didn't do that.

As a shortcut in which the point is read as the sum of the whole not facets, this is a good explanation, and all i intended to put,

but,[/b]

A quick google of "food affection" reveals various information but here is a partial base of some of the incident.
This article leads to two other articles about dogs and "training and treats".
http://www.companionanimalpsychology.com/2013/08/is-food-or-affection-better-as-reward.html

This article linked from the above article says...
..."Some scientists have suggested that dogs are uniquely tuned in to human contact; in other words, that in the process of evolving from wolves, dogs have developed special abilities to read human emotions and communication. If this is the case, then social contact with humans should be a valuable reward in training sessions with dogs, but not wolves."...

Of i strongly disagree because it is a relationship not some sort of failure or missing thought or emotion or instinct function.
It simply requires it's method and expression just like language is to translation and comprehension and grammar.
It is also in my opinion one of the greatest examples of science buggering it all up by thinking as a machine not a living being in terms of identifying the concept of being alive !!!.
Alike as once said in a Soviet film ..."the attraction is purely chemical"....

As we continue on things become more bizarre,
Speak of the devil, so to speak, in opening mouths and canids, There was a ceremony performed on the dead called "The opening of the mouth", and was done by a "Jackal god" called Wepwewat and later another absorbed or morphisised into by cultural religious change over a thousand years called Anubis.
Wepwewat and Anubis were in the ancient Egyptian religion the "god of the dead"(among a few other duties) whom received the deads' spirit into the underworld by a journey.
The "opening of the mouth" ceremony is performed to represent(symbolic) assistance to allow nourishment to be enabled in the afterlife and the person to be rejuvenated and reborn.
Given this previous common point of canids licking mouths and sniffing them, it is not a point of actual accurate geographic location(Nubia to Upper Egypt) and whether the Jackal god was modelled by the ancient Egyptian folklore myth being any of or all or any combination Jackal,Ethiopian Wolf(Simien Jackal) or Hybrid of Familiaris(Common House dog) to envisage any Jackals or dogs or wolves in Nubia or Egypt sitting over a corpse of a person and particularly the corpse of an elderly person (whom they probably knew though they were a wild animal) inside their home sniffing their rotting being. Not only this the heat level of that vague geography decrees if anything were rotting, breath or not it would be where moisture is collected, that being in the mouth and throat.
One thing that will not entirely be easy to explain however in establishing that tradition of opening of the mouth from the previous scene is that of why it relates afterlife mints because you would need to receive a regurgitated meal from a dog to conclusively understand that may have been exactly what some pet wolf or jackal did 8000yp and as easily for many Nubian and Badari on a regular basis. There were no locks or proper doors on their houses and the area would contain anything from pure jackals and wolves(Ethiopian or Arabian) and dogs to hybrids that either roamed or were pets.
(I have actually received such a meal from my pet Dingo(Coincidentally he was named "Abubus") in 1986-7 while lying in bed one morning and near drowned!).

evan_au: and seems to focus on licking my mouth. (Yuk!)

Yum! what have you been eating? what's the new flavour?
No great difference between dogs sniffing each others sphincters.
They have extremely sensitive organs for sensing and collecting information and data of the environment around them, and their programmed instinct causes them to continually examine for the tiniest piece of change to add to their data repository of information on local government garbage handling.
This helps them survive as it is part of their natural tool set to be "driven" to behave that way compulsively and rudely.

But ultimately, is it licking your face or mouth or the fact their "tongue gets into your mouth" just as they sometimes ram their nose into your mouth or open your jaw with their tongue or nose if your lying down?
If you don't stop them they will just sit there with their nose in the corner of your mouth just sniffing. That in my mind says it was it's type of perfume and as much affection.

[cheryl j]

An interesting article about MRI scans on the brains of dogs, showing how they respond emotionally to different types of human speech and dog sounds.

https://www.sciencenews.org/article/people-dogs-have-brain-areas-respond-voices

[nicephotog]

cheryl j: http://www.cell.com/current-biology/retrieve/pii/S0960982214001237
http://www.sciencedirect.com/science/article/pii/S0960982214001237

(!31.50 - i'm after a book from Cairo international press on an old obscurity i recently mentioned , should be interesting when i get around to them)

The following quote below(...""...) from the above links [1]and[2] takes much longer if what scientists of the field of evolution deem to define as a time sector of evolving development to a registerable change of species(apart sample problems of fossils).
e.g.
- short (to a sub species specialist but principly identical) = 1/2 million years
- standard change (some facet of its survival mechanics and environment region has shifted(demography) , now different but only similar example of a previous) = 1 million years
- definite redevelopment (mechanically only a representation of a previous older shape in all aspects including and environment geography(demography) located differently) = 2 million years

I think it supports what i was suggesting before, "the Grey wolf is probably the true domestic dog" not Canis Familiaris, the latter is simply the old favorite that has been disintegrated by "silver fox syndrome" of breeding and careless breeding in the past 300 years particularly by economics and "puppy farming"(AKA, loosely named description).

Article Quote: ..."During the approximately 18–32 thousand years of domestication [1], dogs and humans have shared a similar social environment [2]. Dog and human vocalizations are thus familiar and relevant to both species [3], although they belong to evolutionarily distant taxa, as their lineages split approximately 90–100 million years ago [4]."...

for this ..."humans have shared a similar social environment [2]"... i would believe humans and canids shared their environment and started to learn each other the moment humans principley became carnivorous (of which i suppose there is no way of knowing whether the canid also or both were partaking of the same delicious crime for the first time born of something to do one afternoon really because there was nothing else to do, but that creature nearby showed fear).

[evan_au (OP)]

one thing that gets poked in your mouth ... is their nose

Perhaps if the dog can't get their nose close to your mouth, they lick to give an extra inch of range?

[nicephotog]

Perhaps if the dog can't get their nose close to your mouth, they lick to give an extra inch of range?

100% or "aint no thang".

I have often considered it to be when dogs meet they sniff around each others smelly ends(as much rear) for the point of what they may have been using for food, reasonably much the instinct is primarily for survival by hunting so making a record database of incoming smells that may mean food is most of the point at meeting and greeting, apart sensitivities.