Dogs that repeatedly move their jaws as if chewing on something, when nothing is actually there, are usually responding to discomfort in their mouth, processing an interesting smell, or experiencing involuntary muscle activity. The behavior can be completely harmless or a sign of something that needs veterinary attention, depending on how often it happens, how long it lasts, and what other symptoms come with it.
Something Stuck in the Mouth
The most straightforward explanation is also the most common: your dog has something lodged in or between their teeth, stuck to the roof of their mouth, or wrapped around the base of their tongue. Sticks, bone fragments, pieces of rawhide, hair, and bits of fabric are frequent culprits. String and thread are particularly problematic because a loop can lasso the tongue while the rest gets swallowed, creating a situation that looks like persistent, agitated chewing.
If the chewing motion started suddenly and your dog is also pawing at their face, drooling more than usual, or gagging, a quick visual check of their mouth is a good first step. Gently lift the lips and look along the gum line, between the teeth, and across the roof of the mouth. Some objects are easy to spot and remove. If you can’t see anything but the behavior continues, a vet can sedate your dog for a more thorough look.
Dental Pain and Gum Disease
Periodontal disease affects the majority of dogs by age three, and repetitive jaw movements can be one of its quieter signs. Bacteria form an invisible film on the tooth surface, above and below the gum line. Over time this causes inflamed gums, deep pockets between the teeth and gum tissue, and damage to the structures holding teeth in place. The whole process is painful, and dogs often cope in subtle ways before they stop eating altogether.
Signs that dental trouble is behind the chewing include bad breath, drooling, bleeding from the mouth, reluctance to chew on favorite toys, and changes in eating habits. Some dogs carry food away from the bowl and drop it on the floor before eating. Others become withdrawn or unusually irritable. A fractured tooth or an abscess below the gum line can produce the same phantom chewing, since the dog is essentially working their jaw trying to relieve pressure or discomfort they can’t reach.
Processing a Smell
Dogs have a specialized scent organ called the vomeronasal organ, located above the roof of the mouth just behind the front teeth. When your dog encounters a particularly interesting smell, especially pheromones or hormones from another animal’s urine or genital area, they may chatter their jaw, smack their lips, or make quick chewing motions to push air across this organ. It’s the canine version of a behavior seen more dramatically in horses and cats, where they curl back their upper lip.
This type of chewing is brief, situational, and often accompanied by intense sniffing or a strange grimace that can look like a smirk. It’s completely normal. You’ll typically notice it outdoors, after meeting another dog, or when your dog finds a spot on the ground worth investigating. If the behavior only happens in these contexts and passes quickly, there’s nothing to worry about.
Focal Seizures and Fly Biting
Repetitive chewing that seems involuntary, where your dog appears zoned out or unaware of their surroundings, may be a type of focal seizure. Unlike the full-body convulsions most people picture when they think of seizures, focal seizures affect only one part of the brain and can show up as isolated jaw movements, lip smacking, or snapping at the air as if catching invisible flies.
This “fly biting” or “fly snapping” syndrome has been recognized in veterinary neurology for decades. Dogs snap at something that isn’t there, sometimes tracking it with their eyes first. The episodes can come and go unpredictably. In one early study of eight dogs with jaw snapping, periods of spontaneous remission lasted anywhere from less than a week to five months, with the behavior returning weeks to years later. Some dogs also licked their paws excessively, became agitated, or showed other behavioral changes between episodes.
Certain breeds are genetically predisposed to focal seizures. Belgian Shepherds, Standard Poodles, Hungarian Vizslas, and Border Collies all show high rates of seizures that start as focal events. In Standard Poodles, 93% of dogs with idiopathic epilepsy experienced focal seizures rather than generalized ones. That said, focal seizures can occur in any breed at any age.
If your dog’s chewing episodes look involuntary, happen when they’re resting, or are accompanied by staring, twitching, drooling, or confusion afterward, recording a video for your vet is one of the most useful things you can do. Focal seizures are often manageable once properly diagnosed.
Nausea and Gastrointestinal Discomfort
Dogs that feel nauseous often smack their lips, swallow repeatedly, and make chewing motions. This is the body’s way of producing extra saliva to protect the throat and esophagus in preparation for vomiting. If the nausea passes without vomiting, you may only see the jaw movements and some drooling.
Common triggers include eating too fast, dietary changes, motion sickness, or a mildly upset stomach. If the chewing happens mostly after meals or in the car and resolves on its own, nausea is a likely explanation. Persistent nausea with repeated episodes over several days, especially paired with loss of appetite or lethargy, points to something deeper going on in the digestive tract.
Canine Distemper
One serious cause worth knowing about is canine distemper, a viral infection that can produce a very specific symptom called “chewing gum fits.” These are seizures involving salivation and rhythmic chewing movements of the jaw, caused by the virus damaging the brain. The neurological signs also include localized muscle twitching that can affect the face, limbs, or other body parts.
Distemper is rare in vaccinated dogs, so this is primarily a concern for unvaccinated puppies, rescue dogs with unknown vaccine histories, or dogs with compromised immune systems. Other symptoms typically appear first, including fever, nasal discharge, coughing, and eye discharge. If your dog is up to date on vaccinations, distemper is very unlikely to be the cause.
Anxiety and Compulsive Behavior
Some dogs develop repetitive jaw movements as a self-soothing behavior tied to stress or boredom. This looks different from seizure activity because the dog is fully aware and responsive. They may chew at the air, grind their teeth, or work their jaw when left alone, during thunderstorms, or in situations that make them anxious. Over time, the behavior can become compulsive, meaning it happens even after the original stressor is gone.
Context matters here. If the chewing coincides with situations your dog finds stressful and stops when they’re relaxed and engaged, anxiety is worth exploring. Increased exercise, mental enrichment, and in some cases behavioral support from a veterinary behaviorist can help break the cycle before it becomes entrenched.
How to Tell What’s Going On
Pay attention to three things: timing, awareness, and accompanying symptoms. A dog that chews after sniffing something interesting and then moves on is processing a smell. A dog that suddenly starts pawing at their mouth likely has something stuck or is in oral pain. A dog whose jaw moves rhythmically while they stare blankly is probably having a focal seizure.
Recording the behavior on video captures details you’ll forget by the time you’re at the vet’s office, like how long the episode lasted, whether your dog’s eyes looked glassy, or how they acted immediately afterward. A single brief episode that never repeats is rarely cause for alarm. Repeated episodes, especially ones that increase in frequency or duration, deserve professional evaluation to rule out seizure activity, dental disease, or an underlying illness.