If your dog’s bottom lip suddenly starts drooping and saliva begins dripping from one side of its mouth, it may indicate a problem affecting the mouth, facial muscles, or nerves.
One side of the lower lip hangs loosely, saliva collects around the mouth, or food and water fall out when a dog eats or drinks.
Although some dogs naturally have loose or droopy lips, a new change accompanied by excessive drooling deserves attention.
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Dog Bottom Lip Drooping and Drooling: Why It Happens
A dog’s bottom lip may droop and cause excessive drooling when the muscles controlling the mouth become weak, the facial nerves are affected, or pain and irritation inside the mouth interfere with normal lip movement and swallowing.
Facial nerve paralysis is an important possibility when one side of the lip hangs lower than the other, particularly if saliva escapes from the same side.
Dental disease, oral injuries, foreign objects, and jaw or nerve disorders can also cause drooling and changes in the appearance of the mouth.
The distinction between a naturally loose lip and a newly drooping lip is important. If your dog’s mouth previously looked symmetrical but one side now hangs differently, arrange a veterinary examination immediately. Sudden changes in facial movement should not be dismissed as normal drooling.
Dog’s Bottom Lip Drooping and Drooling: Causes
1. Facial Nerve Paralysis
Facial nerve paralysis is one of the important conditions to consider when a dog’s lip suddenly starts drooping and saliva escapes from one side of the mouth.
The facial nerve controls the muscles responsible for facial movement, including the lips, ears, and eyelids.
When this nerve is damaged or stops functioning properly, one side of the face may become weak or paralyzed.
You may notice that the lower or upper lip hangs loosely, saliva drips from the affected side, and food becomes trapped between the lip and teeth. A dog may also be unable to blink normally or move one ear.
Possible causes include middle or inner ear infections, trauma, hypothyroidism, and cases where the underlying cause cannot be identified.
Facial nerve paralysis may affect one or both sides of the face and requires veterinary investigation.
Related: Dog’s mouth drooping on one side (Causes and treatment)
2. Dental Disease or Tooth Abscess
Dental problems can cause excessive drooling and changes in how a dog holds its mouth.
An infected tooth, severe gum inflammation, or an abscess may cause pain that makes your dog reluctant to move its lips normally.
You may notice bad breath, swollen gums, difficulty chewing, dropping food, or sensitivity when the face is touched.
Some dogs drool more on the side where the dental problem is located. However, a true one-sided facial droop may indicate an additional nerve or muscle problem.
A veterinary examination of the teeth and gums can help identify infections, damaged teeth, and other painful conditions.
Read more: Tooth Abscess in Dogs (Signs, causes and treatment)
3. Oral Injury or Something Stuck in the Mouth
A cut, ulcer, burn, or foreign object inside the mouth can cause drooling and changes in how your dog holds its lips.
For example, a small piece of plant material, wood, or another object may become trapped between the teeth, gums, or roof of the mouth.
A dog may drool excessively, repeatedly lick its lips, paw at its mouth, or struggle to chew.
If the injury affects the lower lip, you may notice swelling or an uneven appearance. Do not pull out anything deeply embedded in the mouth; have your veterinarian examine it.
4. Trigeminal Nerve Dysfunction (Dropped Jaw Syndrome)
The trigeminal nerve controls the muscles used to close the jaw and provides sensation to parts of the face.
When this nerve is affected, a dog may suddenly become unable to close its mouth properly.
This condition is called idiopathic trigeminal neuropathy, sometimes referred to as dropped jaw syndrome.
Affected dogs may have an open or hanging jaw, excessive drooling, and difficulty eating or drinking because they cannot close their mouths normally.
Unlike facial nerve paralysis, which affects facial expression and lip movement, trigeminal neuropathy primarily affects jaw closure.
Many dogs recover over several weeks with supportive veterinary care, but sudden jaw weakness must be assessed because fractures and other neurological conditions can cause similar signs.
5. Middle or Inner Ear Infection
An infection involving the middle or inner ear can affect the facial nerve because it travels close to the ear structures.
If the infection damages or inflames this nerve, your dog may develop a drooping lip, reduced facial movement, and drooling on the affected side.
Other signs may include head shaking, scratching one ear, an unpleasant ear smell, head tilting, or difficulty maintaining balance.
Some dogs show facial changes before owners notice obvious ear discomfort. If your dog has a drooping lip alongside ear symptoms, an examination of the ears is particularly important.
6. Jaw Injury or Temporomandibular Joint Problems
The temporomandibular joints connect the lower jaw to the skull and allow your dog to open and close its mouth.
An injury, dislocation, or other joint problem may interfere with normal jaw movement and cause drooling.
You may notice that your dog cannot close its mouth comfortably, struggles to chew, holds its jaw at an unusual angle, or reacts when attempting to eat.
A jaw injury may also cause swelling, facial asymmetry, or visible discomfort. If the change occurred after an accident or rough impact, seek prompt veterinary attention.
7. Oral Growths or Masses
Growths involving the gums, tongue, lips, or other mouth tissues can interfere with normal lip movement and saliva control.
Depending on their location, they may cause one side of the mouth to look swollen or uneven, increase drooling, or make chewing uncomfortable.
Bad breath, bleeding, difficulty swallowing, or reduced interest in food may be noticed.
Not every oral lump is cancerous, but any new swelling or growth inside the mouth should be examined by a veterinarian.
8. Poisoning or Exposure to Irritating Substances
Certain harmful substances can cause excessive saliva production, mouth irritation, or neurological changes.
Depending on the substance, a dog may develop drooling, vomiting, tremors, weakness, difficulty swallowing, or unusual behavior.
If your dog suddenly develops heavy drooling and changes in mouth movement after possible exposure to a harmful substance, seek emergency veterinary care. Do not wait for additional symptoms.
9. Generalized Neurological or Muscle Disorders
Some neurological and neuromuscular conditions can affect the muscles involved in chewing, swallowing, and controlling the mouth.
Depending on the condition, your dog may develop facial weakness, difficulty swallowing, excessive drooling, or weakness in other parts of the body.
For example, certain neuromuscular disorders can make it difficult for a dog to maintain normal jaw movement.
If the drooping lip is accompanied by weakness, difficulty walking, changes in swallowing, or other neurological signs, urgent veterinary assessment is important.
Dog Bottom Lip Drooping and Drooling on One Side
When the bottom lip droops on only one side and saliva escapes from that same side, facial nerve paralysis becomes an important possibility.
The facial nerve controls the muscles responsible for normal lip movement. If one side is affected, the lip may hang loosely, allowing saliva to escape instead of remaining inside the mouth.
You may also notice that one ear hangs lower, the nose appears slightly uneven, or your dog cannot blink normally on the affected side.
An ear infection, trauma, or idiopathic facial nerve paralysis may be responsible. A veterinary examination is needed to distinguish between these conditions.
Dog Bottom Lip Drooping and Drooling but Acting Normal
A dog may have a drooping lip and continue eating, walking, and playing despite having an underlying problem.
Some dogs with facial nerve paralysis remain otherwise alert and active. They may show little change in appetite or energy, even though their facial movements are abnormal.
However, acting normally does not rule out a neurological condition. The inability to blink properly can also expose the eye to dryness and damage, even when the dog appears comfortable.
If the lip drooping is new, arrange a veterinary examination promptly rather than waiting for your dog to become lethargic.
Dog Bottom Lip Drooping, Drooling, and Not Eating
When a drooping lip and excessive drooling occur alongside reduced appetite, pain, or difficulty using the mouth, this may be caused by dental infections, oral injuries, jaw problems, or neurological conditions that make chewing or swallowing difficult.
Your dog may approach its food but struggle to pick it up, drop food from the mouth, or walk away after attempting to eat.
If your dog cannot swallow normally, do not force food or water into its mouth. Seek prompt veterinary care, particularly if swallowing difficulty or choking is present.
Dog’s Bottom Lip Drooping and Drooling: What to Do
1. Arrange a Veterinary Examination
Contact your veterinarian immediately, particularly if the drooping started suddenly or affects only one side of the mouth.
Explain whether your dog can close its mouth, chew normally, blink both eyes, and move its ears equally.
These details can help the veterinarian determine whether the problem involves the facial nerves, jaw, or mouth.
2. Check for Other Facial Changes
Observe whether one ear hangs lower, one eye remains partly open, or food and saliva collect around one side of the mouth.
You can take a photograph or short video showing the changes to help your veterinarian assess the symptoms.
Avoid repeatedly manipulating your dog’s lips or jaw.
3. Look for Signs of Dental or Oral Problems
If your dog allows you to do so comfortably, look for visible swelling, bleeding, damaged teeth, or unusual growths around the lips and gums.
Do not force your dog’s mouth open, particularly if it appears painful or cannot close its jaw properly.
4. Keep Your Dog Comfortable
If chewing is difficult but your dog can swallow normally, ask your veterinarian whether temporarily offering soft food is appropriate.
Keep fresh water accessible, but do not force your dog to drink if it has difficulty swallowing.
5. Protect the Affected Eye
If your dog also has difficulty blinking or closing one eye, the eye may become dry and irritated.
Contact your veterinarian promptly about appropriate eye lubrication and protection. Do not use human eye medication without veterinary advice.
6. Avoid Unprescribed Medication
Do not give human painkillers, leftover antibiotics, or other medication without veterinary instructions.
The appropriate treatment depends on whether the problem involves a nerve, dental infection, jaw injury, or another condition.
When to Call or Visit Your Vet
A newly drooping bottom lip accompanied by excessive drooling needs immediate veterinary assessment, even if your dog is otherwise behaving normally.
Seek emergency veterinary care if you notice:
Sudden inability to close the mouth.
Difficulty swallowing or choking.
Heavy drooling accompanied by weakness or tremors.
Difficulty breathing.
Sudden facial weakness involving several areas.
Inability to blink or close one or both eyes.
Severe jaw pain or suspected jaw injury.
Collapse, seizures, or difficulty walking.
Suspected poisoning or exposure to a harmful substance.
Do not delay care if your dog cannot swallow normally or has difficulty breathing.
Dog’s Bottom Lip Drooping and Drooling: Treatment
Treatment depends on the underlying cause. Your veterinarian will examine the mouth, teeth, jaw, ears, and facial movements and assess the ability to blink, chew, and swallow.
Blood tests, thyroid testing, dental X-rays, or advanced imaging such as CT or MRI may be recommended depending on the findings.
If facial nerve paralysis is diagnosed, treatment focuses on identifying and managing the underlying cause, while lubricating eye medication may be needed if blinking or tear production is affected.
Dental infections require appropriate dental treatment, while jaw injuries and trigeminal neuropathy need condition-specific supportive care.
Key Takeaway
A dog with a drooping bottom lip and excessive drooling may have facial nerve paralysis, dental disease, an oral injury, a jaw problem, or another neurological condition.
When one side of the lip hangs lower and saliva escapes from that side, facial nerve dysfunction is an important possibility. If your dog cannot close its mouth properly, trigeminal neuropathy or a jaw problem may also need investigation.
Even if your dog is still eating and playing, a new change in facial movement should not be ignored.
Arrange a veterinary examination promptly to identify the cause and protect your dog’s ability to eat, drink, blink, and swallow comfortably.
