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In the human world, lip smacking is something we do when we open and close our mouth loudly to express a strong desire to eat something we like, but in the dog world, lip smacking can take place for many other reasons. 

Some dog owners may find the behavior concerning especially when a dog licks his lips excessively, while others may find it downright annoying.

 By the way, if you are terribly bothered by those lip smacking noises your dog makes, there are chances you may have a condition known as "misophonia" which literally means "hatred of sound" and can involve specific noises produced when someone eats, yawns or when dogs smack their lips. 

Back to dogs, let's discover six surprising reasons why dogs smack their lips.

dog lip smacking

Yum! Dog licks his chops at the sight of his food.

1) Anticipation of Food

Just like us, a dog's mouth may water when he sees food, smells food or even thinks about food. This collection of saliva in a dog's mouth may cause him to drool, which is often seen in dogs with heavy jowls, but sometimes dogs may just discreetly smack their lips to collect the excessive saliva that collects laterally and prevent it from seeping out.

In this case, the lip smacking behavior occurs when there is something in the dog's environment that has to do with food. You're likely to see your dog smack his lips therefore when you're cooking something or when you're prepping your dog's meal.

Surprising fact: Your dog may even smack his lips when no food is around. When Russian physiologist Ivan Pavlov started studying the digestive process in dogs, he noticed how the dogs salivated naturally when food was presented, but what was really surprising is that the dogs started salivating even upon the mere sight of the white lab coat of the experimental assistants! 

Basically, the dogs started associating food with the lab assistant's coat so they drooled upon seeing it and at some point even upon hearing the lab assistant's foot steps!

So if you ever clicker trained your dog, don't be surprised if he smacks his lips when you get the clicker out or upon clicking it, even before you give a treat. From your dog's perspective, the clicker is what dog trainers call a secondary or conditioned reinforcer, meaning that the dog has learned to associate it with treats. 

Its mere presence can trigger a lip smacking event. Same goes with seeing Aunt Molly. 

If every time Aunt Molly meets your dog she gives him a treat, just seeing her may elicit a lip smacking episode as he anticipates food from her!

2) A Bout of Nausea

dog nausea

Just before people or dogs vomit, saliva accumulates in the mouth and this may trigger lip smacking in dogs and drooling or repeated swallowing in humans.

Why this saliva accumulates in the mouth before vomiting is not entirely clear, but according to Science Focus, there is belief that it may be a protective measure to prevent the throat, mouth and teeth from being harmed by the highly acidic stomach contents when they're brought up.

Fortunately, most cases of dog lip smacking from nausea resolve after the dog has vomited, but sometimes the nausea may go on for some time and the dog may be repeatedly gulping down saliva.

Surprising fact: dogs can get acid reflux too! Small dogs are particularly prone to it as they have tiny stomachs and their metabolisms are so fast that their stomachs remain empty for some time. When their stomach is empty, they produce gastric acid, but since it's not absorbed by food, it stays in the stomach, irritating the lining and causing nausea and vomiting of yellow bile, explains veterinarian Dr. Fiona.

dog tooth pain

3) A Mouth Problem

When we have mouth or tooth pain, we may look inside the medicine cabinet to address the pain and make an appointment with the dentist. 

Dogs have no way to tell us about their problem, other than showing signs of discomfort such as lip smacking and drooling, dropping food as they eat and pawing at the mouth.

Problems that may affects a dog's mouth or tooth may include periodontal disease, objects embedded in the dog's mouth or problems with the salivary glands. If you live in an area where there are foxtails, consider that these pesky awns may have lodged somewhere into your dog's mouth or throat causing lots of discomfort, lip smacking, drooling and gagging.

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Surprising fact: In the world of fairy tales, kissing a frog may turn it into a prince, but in the dog world kissing the wrong type of toad may lead to lip smacking and foaming at the mouth and may even turn life threatening if veterinary care isn't sought in a timely manner.

Problems start when a dog licks a giant toad or a Sonoran desert toad, two species that secrete toxic substances as a defense mechanism. Along with foaming at the mouth, affected dogs may develop a high temperature, red gums, trouble breathing, abnormal heart rhythms, seizures and even death. 

The Pet Poison Helpine recommends rinsing the mouth out and immediately contacting the vet.

4) A Sign of Pain/Illness

As a species that relies of words and vocalizations, us humans often assume dogs will show their pain though whines, whimpers and yelps, but that's not always that way. Many dogs show subtle signs of pain that are often missed by dog owners or attributed to other things others than pain. Other than nausea, lip smacking can be a sign of pain explains veterinarian Dr. Jake Tedaldi in the book: "What's Wrong with My Dog?" Once the pain is taken care of, the lip smacking behavior should therefore resolve.

Surprising fact: there are several other physical ailments that could trigger lip smacking in dogs. For example, liver and kidney disease can cause lip smacking, and so can dehydration, further suggests Dr. Tedaldi. In some cases, partial seizures may also cause a dog to lick the air and snap, as if catching imaginary flies.

dog lip licking

5) A Calming Signal

In dogs, licking the lips can be what Roger Abrantes calls a "pacifying behavior." Dogs basically engage in this behavior to diffuse a perceived threat using the lip smacking action as an appeasing signal. It can be seen in dogs who are stressed, anxious or nervous about an interaction or when there is some type of conflict going on.

Many dogs smack their lips when they are being photographed (it makes some dogs uneasy) or when an owner trips on them. As with other behaviors, it's important to look at context as things can get blurry at times. A person may assume a dog may smack its lips from nervousness when starting a training session, but it could also mean the dog is anticipating treats. Patrica McConnell in her blog suggests a way to distinguish the two.

"Usually, (but not always) licking in anticipation of food involves the tongue moving laterally, to the side of the dog’s mouth, while in other types of lip licks the tongue moves straight forward." ~ Patricia McConnell

Surprising fact: Lip licking behavior has likely evolved with the dog because it has proven to prolong the dog's life increasing its chance of surviving and reproducing, suggests Abrantes. The behavior must have therefore puts roots as it helped the dog survive conflicts without incurring in physical harm.

6) Attention Seeking Behavior


Last but not least, lip smacking behavior may occur at times because the dog notices that it gets the owner's attention. After ruling out any medical causes, this may be a possibility if every time your dog smack his lips, you turn to look at him or talk to him.

The lip smacking behavior therefore puts roots because it has been accidentally reinforced by the owner. Dogs who look for attention are often dogs who are socially deprived spending the majority of the day alone and craving any form of attention when the owner comes home.

As with other behaviors, it's important to look at context. If it happens only in presence in the owner, it's likely attention-seeking behavior. By recording the dog's behavior in the owner's absence, one can probably deduce if it may be attention-seeking behavior or perhaps something else.

Surprising fact: Dogs have been known for engaging in surprising behaviors just for the sake of attention, even pseudo-medical attention-seeking behaviors, like faking lameness or face scratching, explains Dr. Nicholas Dodman. And if you were wondering, consider that even negative attention such as reprimanding the dog telling him to stop may qualify as attention to a dog who is craving attention. The best approach is to totally ignore.

"Even telling your dog to stop, or reprimanding him, can be rewarding for some dogs. The principle here is that some attention, even negative attention, is better than no attention at all." ~Dr. Nicholas Dodman

Disclaimer: this article is not meant to be used as a diagnostic tool or as a substitute for professional veterinary or behavioral advice. If your dog is smacking his lips, see a vet for proper diagnosis and treatment.

Six Causes of Lip Smacking in Dogs


  • What's Wrong with My Dog? by Dr. Jake Tedaldi, Fair Winds Press (August 1, 2007)
  • Science Focus, Why do we salivate before we vomit, by Luis Villazon, retrieved from the web on April 30th, 2016
  • Roger Abrantes, Pacifying Behavior, Origin Function and Evolution, retrieved from the web on April 30th, 2016
  • The Other End of the Leash, What Does Licking Mean? by Patricia McConnell, retrieved from the web on April 30th, 2016
  • Pet Place, Attention-Seeking Behavior in Dogs, by Dr. Nicholas Dodman, retrieved from the web on April 30th, 2016

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