Mouth Sores in Dogs

Dog with mouth open
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Noticing a new sore, lump, or lesion on your dog's mouth can be alarming. It may appear on the lips, inside on the gums, or even on the tongue, and there are many possible causes, including dental and autoimmune diseases. However, some dogs may develop sores for less-serious problems, or it could be a benign growth. Diagnosing mouth ulcers isn't simple, so it's important to take your dog to the vet for an exam when you see one.

Why Do Dogs Have Mouth Sores?

If you notice your dog is suffering from a mouth sore, there are some questions to take into consideration so you can help your vet diagnose and treat the issue. Is your dog clearly in pain? Is it drooling, reluctant to eat, "chattering" its teeth, or lethargic?

Take note of and talk to your vet about these and any other abnormal behaviors during an exam. Mouth ulcers can be caused by a number of different health problems and, if left untreated, may increase the likelihood of secondary infections and irritations of the face and lips.

  • Dental Disease: Gum lesions and other dental diseases may be the cause of a mouth ulcer. This may be accompanied by a loss of some hair.
  • Weepy Eyes: If it's not addressed, excessive tearing or eye drainage may lead to sores anywhere on the face because it is irritating the skin 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 who do not yet have a fully developed immune system.
  • Cancer: Oral tumors on the gums, lips, tongue, and lymph nodes may be either cancerous or benign. If left untreated, the tumor may become malignant, worsening to a life-threatening stage.
  • Gingival Hyperplasia: Appearing as an overgrowth of gum tissue, this can look like a small tumor. It is typically benign but can be biopsied 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. These are parts of the body where skin meets mucous membranes, such as the moist tissues of the mouth, nose, eyes, vulva/prepuce, and anus.

    Pemphigus vulgaris is both the rarest and the most severe form. It specifically affects mucocutaneous junctions, such as the lips. Additional symptoms include fever, depression, and anorexia. The skin may also be affected—often in the form of itchy or painful skin—though this is usually mildly involved in the overall problem.

    Ulcers and sores resulting from these diseases can become secondarily infected with bacteria, creating more of a problem. Antibiotics may help, but will not cure this condition, which is caused by an "overactive" and errant immune system.

    Diagnostic Processes

    Once you get to the vet's office, she will do a thorough exam of the mouth ulcer and your dog's overall health to narrow down the possible causes. It's likely that a biopsy of the affected tissue will be taken to obtain an accurate diagnosis for pemphigoid and other diseases.

    For additional information, you may also want to schedule a consultation with a veterinary dermatologist. Another recommendation is to make an appointment at a veterinary teaching hospital for a workup.


    Once a diagnosis is established, the treatment will focus on the cause. For instance, if it's an autoimmune disorder, treatment will be aimed at controlling the immune response using immunosuppressive drugs. Proper diagnosis is key, however; if the cause of the lesions is an infection as opposed to an immune-mediated process, immunosuppressive drugs are contraindicated and will not treat the actual cause.

    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.

    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.

    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.

    The other preventative steps you can take include the basic healthcare needs for your dog. A nutritious diet and regular veterinary check-ups can help you keep your dog as healthy as possible and reduce its risks of serious health problems. While you may not be able to prevent everything, in the least it can lead to early detection of potential issues. That can make a significant difference in successful treatment.