What Are Those Sores on My Dog's Mouth?

Dog with mouth open
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If you notice your dog is suffering from mouth ulcers, there are some questions to take into consideration in order to help diagnose and treat the issue. Is your dog clearly in pain? Is he drooling, reluctant to eat, "chattering" teeth, or lethargic? If he has lost some hair this could be related to gum lesions or dental disease.

Dental disease, weepy eyes, or facial skin folds may increase the likelihood of infections and irritations of the face and lips.

Autoimmune Disorders

There is a group of diseases called pemphigus that have several forms (foliaceus, vulgaris, erythematosus, vegetans, and bullous pemphigoid) and vary in location and severity.

These diseases are a result of an autoimmune process; the body's own immune system attacks the "cement" of the skin layers, creating blisters, sores, crusts, and ulcerations on the skin and mucocutaneous junctions (where skin meets mucous membranes, the moist tissues of mouth, nose, eyes, vulva/prepuce, and anus).

Pemphigus vulgaris, while rarer than other forms, is specific for the mucocutaneous junctions, such as lips. The skin may also be affected, usually mildly involved.

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


A biopsy of the affected tissue is recommended to obtain an accurate diagnosis for pemphigoid and other diseases. For additional information, you may want to seek a consultation with a veterinary dermatologist.

Another recommendation would be to make an appointment at a veterinary teaching hospital for a workup.


Once a diagnosis is established, treatment is aimed at controlling the immune response using immunosuppressive drugs. Special shampoos, antibiotics, or antifungals are used for any secondary bacterial or fungal infections. Proper diagnosis is key; if the cause of the lesions is an infection (versus an immune-mediated process), immunosuppressive drugs would be contraindicated.

Please note: this article has been provided for informational purposes only. If your pet is showing any signs of illness, please consult a veterinarian as quickly as possible.