What Are Those Sores On My Dog's Mouth?

What Could Be Causing Dog's Lips to Be Ulcerated

Question: Lip Ulcers: What Could Be Causing Dog's Lips to Be Ulcerated

VetMed Forum member NATEWEH asks what would cause his dog's lips to have sores and ulcers. Antibacterial mouth rinses and new dog dishes have been tried, but to no avail. For many types of skin lesions, a scrape or biopsy is often required to accurately diagnose what is going on. This FAQ discusses a group of diseases that can cause lip lesions.

Answer: From the VetMed Forum

NATEWEH writes: "Chihuahua: mouth problems, gums are ok, the lips(?) are ulcer like vet says it's hard to say, possible reaction of the mouth reacting to the teeth? Or possibly a tumor, but doubtful because it's not spreading. I'm not convinced ... we swapped his dishes, started using some anti-bacterial mouthwash and it helped but ran out for now. Just asking for some thoughts, brainstorming, considerations, info, etc.

He's about 3 years old and I'm not looking for a diagnosis, just some opinions, and ideas. The sores are only inside his mouth. He's lost some hair, swollen lymph nodes? Had some teeth pulled as an attempt to "fix" this. Started small, gone up from here.... anyone?

My Reply:

Sorry to hear about your dog's troubles. First question: can you tell if he is painful? Is he drooling, reluctant to eat, "chattering" teeth, or lethargic? You also mentioned that he has lost some hair.

This could be related to gum lesions or dental disease.

You did the right things by swapping out the plastic food dishes and trying the mouth rinse to see if that had any effect. You mention that the mouth rinse helped. I would want to know if that cleared up the problem or just lessened the severity of the lesions.

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

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:

American College of Veterinary Dermatologists (ACVD)  http://www.acvd.org/ *Click on "find Dermatologist" to see if there are any in your area.

Another recommendation would be to make an appointment at a veterinary teaching hospital for a workup: Veterinary Schools in the US and Canada


Once a diagnosis is established, treatment is aimed at controlling the immune response with 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.

Hopefully, this dog and his owner can get some answers about these lip lesions before they become worse. Be persistent and best wishes for getting back to health as soon as possible.

Related Reading:

Autoimmune Skin Disorders (with photos) from the Merck Veterinary Manual

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.