Dog Language #Faces

Even though dogs’ faces and heads come in many shapes and sizes, your dog’s basic facial expressions can tell you a great deal about how he’s feeling.

Your dog can, within limits, vary the shape and size of his eyes or the direction and intensity of his gaze. When your dog is relaxed and happy, his eyes will be their normal shape. Some dogs have round eyes, while others are more almond-shaped. Eyes that appear larger than normal usually indicate that a dog is feeling threatened in some way. He may be stressed by something or he may be frightened. An aggressive dog is also likely to have eyes that look larger than normal. If your dog’s eyes seem smaller than they usually are, this can also mean he’s feeling frightened or stressed. Dogs who are in pain or not feeling well often look as though they’re squinting their eyes. Dogs who submissively grin (see below) may also squint their eyes.
The direction of your dog’s gaze can also be telling. Dogs rarely look directly into each other’s eyes because this is considered threatening behavior. Yet most dogs learn that it’s okay, even pleasant, to look directly at people. A dog who looks at you with a relaxed facial expression is being friendly and hoping that you’ll notice him. A dog who looks directly at you, actually staring at you with a tense facial expression, is another matter indeed. A direct stare is much more likely to be a threat, and if you’re in close proximity to such a dog, it’s wise to slowly look away. Looking away is what dogs do when they don’t want to appear threatening. A dog who averts his gaze when you look at him is signalling that he’s submissive. It can also indicate that he’s worried about interacting with you. Maybe he’s been scared of people in the past, and so he isn’t very confident about dealing with people now.
If your dog doesn’t look directly at you, but instead looks out of the corners of his eyes so that you see a good deal of the whites of his eyes (the sclera), he might be leading up to an aggressive outburst. Known as “whale eye” this is often seen when a dog is guarding a chew bone, toy or favorite spot. It’s different than the eye of a dog who, for instance, is resting with his head and opens his eyes to give you a sideways glance. In this case, he won’t appear rigid or tense, and you won’t see much of the whites of his eyes.   

http://www.aspca.org/pet-care/virtual-pet-behaviorist/dog-behavior/canine-body-language