Is there a sight in the world more cheering than seeing a dog smile? Is there a sensation as pure and comforting than baby puppy kisses? Even asking those questions aloud suffuses me with a warm inner glow. But wait a moment; does the curl of a dog’s mouth and the glimpse of a dog’s teeth really constitute a proper smile? And hold on; I’ve never seen a dog pucker up! “Kisses” are just what we called being licked by a dog.
If you’ve ever spent a significant amount of time fruitlessly obsessing over the contours of your dog’s mouth, you’re in luck! We’ll explore the most pressing questions about dog mouths, and learn a few facts about dog anatomy and behavior in the process. Dogs certainly cannot talk, but did you know that their mouths can still tell us how they are feeling? Our tour around the outer rim of a dog’s oral cavity will attempt to address the following queries:
Since there are four further questions about dog mouths and lips, it’s safe to assume that yes, dogs do have lips, but they’re very different in form and function than the ones that adorn human faces. We can easily tell our upper lip from our lower lip, but our jaw lines are so distinct from each other, it’s no wonder people doubt that dogs have lips at all! Despite apparent differences, one common feature is that, like a human’s lips, a dog’s lips form a continuous protective circle around the outside of a dog’s mouth.
What are dog lips called? In dogs, the lower lip is simply the lower lip, but the upper lips are called “flews.” The flews vary in length from breed to breed. Hound-type dogs, and other heavy-muzzled, big-drooling breeds — Bulldogs and Mastiffs among them — have long, low-hanging flews draped over their upper jawline. Along with voluminous facial hair in other dog breeds, the flews can completely obscure a dog’s lower lip.
A major difference between the mouths of humans and dogs is found in the cheeks. A dog’s comparatively longer jawline is balanced by smaller cheek capacity. In humans, cheek and lip muscles work together, providing suction that keeps food and water in our mouths. Run your tongue over the roof of your mouth. The ridges you feel are much larger and more pronounced in a dog’s mouth. A dog’s tongue and hard palate perform a similar function to our cheek-lip combo, but are less precise. This is one reason so much falls out of dog mouths when they eat and drink.
Have you ever noticed the finger-like protrusions lining a dog’s lower lip? No matter how deeply I dug into dog anatomy, I could not find a satisfying answer to what they are, what they’re called, or what purpose they serve. The only reliable mention I came across was in Auguste Chauveau’s The Comparative Anatomy of the Domesticated Animals (1873), which notes that the dog’s “lower lip is always scalloped on its free border near the commissures.” More on the commissures below!
Anyone who pays close attention to dog physiology will have noticed that a dog’s nose and the outer lining of their lips are typically the same color. A quick peek around the dog park will tell you that not all dogs have black noses or black lips. Melanin is responsible for all eye, skin, and coat color variations except for white and pink, which are not colors themselves, but expressions of lack of color.
Much like eye color, the darker a dog’s lips and nose are, the more melanin their genetic inheritance makes available to them. The most common nose/lip colors, from least to most melanin, are Isabella (dusty), liver (brown), blue (grey), and black. Genetics are fickle and inconsistent, though, which explains why some dogs have spotted noses and lips. Dogs with darker noses and lips have better natural protection from the sun than their peers.
I mentioned the “commissures” above; this is the technical term for the corners of the lips. You can tell just as much about a dog’s state of mind by the commissures as you can by a wagging tail or an excited bark. There are at least two very common “smiles” that dogs perform. There is the “submissive smile,” which closely resembles a snarl, with the front teeth bared behind tight lips. The next time your dog growls, notice how the corners of their lips tighten up.
The reverse is true of dogs when they are having fun, happy, or even when they’re play-fighting with other dogs. Can dogs smile to convey happiness in the way that humans do? What we might interpret more accurately as a dog smile can be seen in the above Australian Shepherd: The dog’s lips are flaccid, especially at the site of the commissures. Combined with the bright eyes and lolling tongue, the loose contours of the lips tell us that, if this dog isn’t smiling per se, he is at least contented and relaxed.
Similar to smiling, it’s tempting to interpret being licked by your dog, or watching a mother groom a litter of puppies, as signs of pure affection. Unfortunately, an interpretation is all it is. I’ve investigated the question of why dogs lick people before. While there are many reasons for dogs to lick humans and each other, none of them bear the romantic or erotic weight we’re asking about here.
It may surprise you to learn that, not only do dogs not kiss each other, but most human cultures don’t either! Indeed, a 2015 study published in American Anthropologist found that romantic kissing is a common practice in less than half of 168 human cultures.
Dogs do not kiss each other, nor can they properly be said to kiss their owners. Our anthropomorphic interpretations of what our dogs do with their mouths doesn’t seem to bother us at all when we’re using our lips to plant kisses of our own on them. Should you kiss your dog? It may be satisfying to pet parents to show affection with smooches for the pooches, but it’s probably not the best idea. Human and canine respiratory illnesses — the common cold or kennel cough — aren’t zoonotic, and can’t infect the other species.
At the same time, just think about all the unseemly places your dog’s tongue has been lately! I am as guilty as anyone of kissing my dog in a happy moment, and other people’s dogs, too, now that I think about it, but I also carry a tube of Listerine mouth spray in my pocket. Do dogs like being kissed? Look to your dog’s lips for clues. Does your dog lick his lips when you approach for a kiss? Do the corners of your dog’s mouth tighten up? Your affectionate pecks might be making your dog nervous! Some humans use their lips to convey affection — romantic, familial, or otherwise — but dogs operate by different rules!