Mouth Sores in Dogs

Dog with mouth open
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Noticing a new sore, lump, or lesion in or around your dog's mouth can be alarming. It may appear on the lips, the gums, or even the tongue. There are many possible causes, including dental and autoimmune diseases, although some dogs develop sores for less-serious reasons, and it could be a benign growth. Diagnosing mouth ulcers isn't something you're equipped to do, so it's important for you to take your dog in for a veterinary exam as soon as you see one.

Why Do Dogs Have Mouth Sores?

If you see that your dog is suffering from a mouth sore, make a note of other symptoms or unusual behaviors you notice to help your vet diagnose and treat the issue. For example, is your dog clearly in pain? Is it drooling, lethargic, or reluctant to eat? Are its teeth chattering?

Mouth ulcers can be caused by a number of different health problems and, if left untreated, may increase the risk of secondary infections.

  • Dental Disease: Gum lesions and other dental diseases may be the cause of a mouth ulcer. This may be accompanied by some hair loss.
  • Weepy Eyes: If it's not addressed, excessive tearing or eye drainage may lead to sores anywhere on the face because it irritates the skin, possibly fostering bacterial growth and causing inflammation.
  • Facial Skin Folds: The natural folds of excess skin on some dog breeds may cause irritation that results in an occasional ulcer.
  • Oral Papilloma Virus: Small oral tumors on the lips, tongue, throat, or gums may be caused by this virus. It typically affects dogs under the age of 2 that don't yet have a fully developed immune system.
  • Tumors: Oral tumors on the gums, lips, tongue, and lymph nodes may be either cancerous or benign.
  • Gingival Hyperplasia: Appearing as an overgrowth of gum tissue, this can look like a small tumor. It's typically benign, but your vet can biopsy it to check for cancer cells.
  • Kidney Disease: Mouth sores are one of the signs of advanced renal failure in dogs with kidney disease.

Autoimmune Disorders

Additionally, there's a group of diseases called pemphigus that have several forms, including foliaceus, vulgaris, erythematosus, vegetans, and bullous pemphigoid. These diseases vary in location and severity.

Pemphigus diseases are the result of an autoimmune process. When the body's immune system attacks the "cement" of the skin layers, it can create blisters, sores, crusts, and ulcerations on the skin. These may also appear on mucocutaneous junctions (parts of the body where skin meets mucous membranes) such as the moist tissues of the mouth, nose, eyes, genitals, and anus.

Pemphigus vulgaris is the rarest and most severe form which specifically affects areas like the lips. Additional symptoms include fever, depression, and anorexia. The skin may also be affected—often in the form of itchiness or pain—though this is usually mildly involved in the overall problem.

Ulcers and sores resulting from these diseases may become infected with bacteria, creating more of a problem.


Once you get to the vet's office, your dog will receive a thorough exam of the mouth ulcer and its overall health to pinpoint the cause. It's likely that a biopsy of the affected tissue will be taken to obtain an accurate diagnosis for pemphigoid and other diseases.

Once a diagnosis is established, the treatment will focus on the cause:

  • Dental problems, including oral tumors caused by the papillomavirus, often require anesthesia so the vet can address the issue. For severe cases, you may be referred to a specialist in veterinary dentistry.
  • Special shampoos, antibiotics, or antifungals may be prescribed for any secondary bacterial or fungal infections. In the case of dental diseases, treatment for these should clear up any lesions and preventive measures in the future may help them from reoccurring.
  • If your dog has dermatitis caused by its skin folds, your vet may recommend hydrocortisone cream, ketoconazole shampoo, or antibacterial ointments to treat or prevent sores. Sometimes, surgery to remove the fold may be required, but this is generally only for extreme cases.
  • For conditions like kidney disease, aggressive and early treatment is best. It often involves medications such as sub-Q fluids and benazepril that help the kidneys function more efficiently.
  • Surgery may be needed to remove a cancerous oral tumor. If it is in an advanced stage, your vet may recommend radiation or chemotherapy as well.
  • If it's an autoimmune disorder, treatment will be aimed at controlling the immune response using immunosuppressive drugs. Antibiotics may help with the secondary infections but won't cure the underlying condition, which is caused by an overactive immune system.

How to Prevent Mouth Sores

Maintaining your dog's oral hygiene can prevent a lot of the dental problems and infections that cause oral ulcers. Try to clean your dog's teeth on a regular basis. While you're doing that, take time to examine your dog's entire mouth, looking for signs of irritation or abnormalities. The more often you do this, the easier it will be to detect changes early, which can help with treatment.

Some dogs with a natural excess of facial skin may require more regular bathing or ointments to prevent problems. Watching your dog's eyes for any seepage and taking steps recommended by your vet may also prevent ulcers from developing.

Other preventive steps you can take include the basic healthcare needs for your dog. A nutritious diet, sufficient exercise, and regular veterinary checkups can help keep your dog as healthy as possible and reduce its risks of serious health problems. While you may not be able to prevent everything, you can get a head start on early detection of potential issues.

If you suspect your pet is sick, call your vet immediately. For health-related questions, always consult your veterinarian, as they have examined your pet, know the pet's health history, and can make the best recommendations for your pet.