Dog Mouth Ulcer: Symptoms, Causes and Treatment

Just like people, dogs can get painful mouth ulcers too. These are sores inside your dog’s mouth that can make it hard for them to eat, chew, or even play. In this blog, we’ll explore what causes oral ulcers, how to spot them early, and what you can do to treat and prevent them. Whether your dog has bad breath, a decreased appetite, or visible mouth sores, this guide gives you clear answers.

What Is a Dog Mouth Ulcer?

A mouth ulcer is a raw, crater-like sore on the oral mucosa—that thin skin covering the tongue, gums, lips, or inner cheeks. Because the area is packed with nerves, even a tiny sore can cause sharp oral pain. Vets use special names for certain patterns:

• Kissing ulcers (or contact ulcers) form where the sore on one surface “kisses” the opposing tissue, rubbing every time the dog chews or pants.

• Canine chronic ulcerative stomatitis and chronic ulcerative paradental stomatitis describe widespread immune-linked sores around many teeth.

The British Veterinary Association lists dental plaque and ignored dental disease as major triggers for these ulcers and urges routine mouth checks for every pet owner. Unlike a chipped tooth or small cut, a true ulcer looks sunken with pale or red edges and may ooze. Catching that localized ulcer early stops it from turning into severe inflammation and spares your dog weeks of pain.

Common Symptoms of Mouth Ulcers in Dogs

Dogs hide pain well, so owners need to spot small changes first. Key clinical signs of ulcers in dogs include:

• Excessive drooling or saliva with blood

• Bad breath (halitosis) – often due to oral bacteria or diseased teeth

• Decreased appetite or dropping food

• Pawing at the mouth or licking the lips constantly

• Visible mouth sores, especially on the gum tissue, tongue, or lip folds

• Swelling in the face or around the lymph nodes

The PDSA symptom checker warns that mouth pain often shows as subtle behaviour change long before a dog stops eating

What Causes Mouth Ulcers in Dogs?

Ulcers rarely appear without a push. Below are the top triggers UK vets see:

• Chronic periodontal disease – Hardened dental plaque and tartar rub the gums, causing sores and feeding bacterial infection. Vet Times notes that calculus scraping the cheek can set off a deep ulcer.

• Metabolic disease – Dogs with advanced kidney disease or liver failure build up toxins that irritate oral tissues, leading to mouth inflammation and ulcers.

• Autoimmune disease – Conditions like lupus erythematosus prompt the immune system to attack the mouth, creating widespread, painful lesions.

• Oral tumors – Growths such as squamous cell carcinoma outgrow their blood supply, causing ulcerated patches.

• Trauma and chemicals – Sharp bones, sticks, or household cleaners can burn or cut the buccal mucosa and upper lip.

• Poor nutrition & lip fold dermatitis – Soft, sticky food left in the lip folds breeds bacteria that erode skin.

Knowing which trigger fits your dog helps your vet design the right plan—from teeth cleaning to tumour removal.

When to See a Vet

While some localized ulcers may heal on their own, many don’t. If your dog has severe inflammation, constant oral pain, or refuses food, it’s time to call the vet.

• Ulcers that last more than 3–5 days

• Ulcers with pus or swelling

• Blood in saliva or from the oral tissues

• Lip wounds, kissing lesions, or ulcers on the upper lip

• Fever or signs of infection

• Sudden changes in behaviour or eating habits

Your vet may carry out a complete blood count, oral exam, or even oral surgery if they suspect oral tumors or immune-related disease.

Home Care for Mild Mouth Ulcers

If your dog’s ulcers are mild and not linked to a serious underlying disease, you may be able to help at home—with vet advice.

• Rinse the mouth with warm salt water (never use human antiseptics)

• Feed a soft diet to reduce pain

• Keep the mouth clean with a chlorhexidine solution (veterinarian-approved only)

• Avoid hard toys or bones until healing

• Encourage gentle chewing with prescription dental diets

Offer dental chews stamped by the Veterinary Oral Health Council once swelling calms; they help scrub away dental plaque that feeds future ulcers. Finally, keep your dog hydrated and rest the jaw—skip tug toys until healing finishes. These steps reduce oral pain and buy time while the body closes the localized ulcer.

Remember: Do not use Bonjela or any human gels. These may contain xylitol or aspirin, which are toxic to dogs.

Vet Treatments for Dog Mouth Ulcers

If your dog has severe inflammation or a dog mouth ulcer that doesn’t heal, a vet must step in. Your vet will first examine your dog’s oral cavity and may run tests like a complete blood count or tissue biopsy to rule out systemic disease, oral tumors, or an autoimmune disease.

• Anti-inflammatory medication to ease pain and swelling

• Antibiotics for ulcers caused by bacterial infection

• Chlorhexidine solution to clean the oral mucosa and fight oral bacteria

• Thorough dental cleaning to remove dental plaque and treat chronic periodontal disease

• Oral surgery in severe cases, such as removing diseased teeth, mouth extractions, or treating oral tumors

• Laser treatment to manage canine chronic ulcerative stomatitis (CCUS) or kissing ulcers

In some affected dogs, a full treatment plan may include immune system support, adequate pain management, or specialised periodontal therapy.

Can Dog Mouth Ulcers Be Prevented?

Yes, you can reduce your dog’s risk of developing mouth ulcers, especially those caused by poor oral hygiene or dental disease. Prevention focuses on keeping a healthy mouth and spotting problems early.

• Daily tooth brushing with dog-safe toothpaste

• Regular professional dental cleaning at the vet

• Feed prescription dental diets to reduce dental plaque

• Give safe chew toys to help clean dog’s teeth naturally

• Inspect your dog’s oral tissues, gum tissue, and lip folds weekly

• Avoid giving sharp bones or sticks that may cause contact ulcers

Dogs with chronic conditions like lip fold dermatitis, metabolic disease, or lupus erythematosus should have more frequent vet checks. Using vet-recommended products reduces the increased risk of oral ulceration.

FunnyFuzzy's Dog Chew Toy

FAQs

How do you treat mouth ulcers in dogs?

Treatment depends on the underlying cause. Mild ulcers may heal with rest, soft food, and clean water. More serious cases need vet treatment with antibiotics, pain relief, or even oral surgery. Avoid home remedies unless advised by a vet.

What does a mouth ulcer look like in dogs?

It appears as a round or ragged sore in the mouth, often white, grey, or red in the centre, with swelling around the edges.

Can you give Bonjela to dogs?

No. Bonjela is not safe for dogs. It contains ingredients like xylitol and salicylates, which are toxic. Always ask your vet for a dog-safe alternative.

Will a dog’s mouth heal on its own?

Minor cuts can close, but true oral ulceration linked to dental disease or metabolic disease needs veterinary care to heal fully.

Conclusion

Mouth ulcers in dogs are more than just an inconvenience—they’re a sign of oral inflammation, infection, or even serious illness. Left untreated, they can lead to painful lesions, bad breath, decreased appetite, or more complex issues like oral tumors or full mouth extractions.

By understanding the clinical signs, staying alert to changes in your dog’s eating or behaviour, and following preventive care, you can help your dog live comfortably.