Mouth Ulcers in Cats – Causes, Symptoms and Treatment

cat mouth ulcers
What is a mouth ulcer?

A mouth ulcer (or mouth sore) is a painful, open sore which can affect the gums and tongue. They are formed when the delicate tissues in the oral cavity are eroded and can be caused by injury, infection or cancer. They are not a disease in themselves, but rather they are a symptom of an underlying condition.

There are a number of causes of mouth ulcers in cats, some of which include:

What do mouth ulcers look like?

Mouth ulcers are small, painful, round, white lesions affecting the mouth including the lips, tongue, and gums.


Calicivirus is a common viral infection in cats which causes “cat flu”, producing upper respiratory symptoms such as sneezing, nasal discharge, rhinitis and mouth ulcers. Cats become infected either directly, via direct contact with the secretions of an infected cat, or indirectly via fomites (inanimate objects such as food bowls and bedding).

Treatment of calicivirus is generally supportive, antibiotics may be prescribed to treat secondary bacterial infection. Removal of nasal and eye discharge with a warm, damp cloth.

Uremic poisoning

Uremic poisoning occurs when nitrogenous wastes build up in the blood due to the kidneys not functioning properly. There are a number of reasons this may happen such as urinary blockage, drugs, and toxins, shock, bladder rupture, but most often the kidneys become less efficient as the cat ages (chronic kidney failure).

Treatment is aimed at addressing the underlying cause (if there is one). Chronic kidney failure is managed by feeding a low protein and phosphate diet, phosphorous binders and fluids to treat dehydration.

Pemphigus complex

A group of rare, autoimmune skin diseases affecting many parts of the body, including the oral cavity. Middle-aged cats are most at risk. There are three forms of the disease, each affecting different layers of the skin. The rarest form, pemphigus vulgaris results in the formation of ulcers in the mouth.

Treatment involves the use of immunosuppressive drugs or steroids in milder cases. Antibiotics may be prescribed to treat a secondary infection.

Feline herpes

Feline herpes is another common viral infection which causes upper respiratory symptoms and oral ulceration in affected cats. Kittens and senior cats are at greater risk than healthy adults.

Treatment is similar to calicivirus, including supportive care such as keeping the eyes and nose clear of discharge, fluids to treat dehydration, antiviral medications and in some cases, antibiotics to treat secondary bacterial infection.


Stomatitis is an inflammation of the mucus membrane in the mouth, the exact cause isn’t known, but it is believed to be immune-mediated, possibly due to oral bacteria, other causes may be an infection, certain medications, and metabolic disease.

Treatment of stomatitis is difficult, finding the underlying cause if possible, cleaning the teeth, antibiotics may be prescribed and corticosteroids to reduce inflammation.

Ingestions of toxins

Some poisons and plants can result in mouth ulcers in cats due to inflammation. Certain plants and chemicals can cause irritation and ulceration.

Treatment depends on the toxin ingested and may include induced vomiting and activated charcoal to prevent further absorption.

Thermal or electrical burns

These are less common to occur in cats than dogs. Thermal burns occur in the mouth when your cat eats something hot and electrical burns occur when your cat chews through an electrical cord. This type of injury is seen most commonly in younger cats.

Treatment for burns includes managing any underlying issues, such as fluid in the lungs, which commonly occurs, cleaning any wounds and antibiotics prescribed.

Rodent ulcer

Rodent ulcers are another inflammatory disorder characterised by the infiltration of eosinophil cells to the affected area. It is seen more commonly in females than males. Most rodent ulcers occur on the lip, but the inside of the mouth can also be affected. It is thought to be caused by an allergic reaction, such as to flea bite sensitivity or food allergies.

Treatment of rodent ulcers includes finding and addressing the underlying cause (if any), such as diligent flea control, switching diets. Steroids may be prescribed to reduce inflammation. If treatment doesn’t work, surgery may be required to remove the lesions.

Oral cancer

Squamous cell carcinoma is a fast-growing oral cancer characterised by swelling of the face and oral cavity, bad breath, bleeding in the mouth, drooling, weight loss and a growth in the mouth, along with possible ulceration. This type of cancer is extremely malignant, quickly spreading to other parts of the body. The tumour is mostly seen in older cats.

Treatment is often limited with this type of cancer, surgery may be performed if the cancer is in the lower jaw along with chemotherapy or radiation therapy.

How is the cause diagnosed?

Your veterinarian will perform a complete physical examination of your cat and obtain a medical history from you. He will need to know how long your cat has had mouth ulcers, are there other symptoms, has he had exposure to plants, chemicals or toxins recently.

Accompanying symptoms may also give your veterinarian an indication of the cause, for example, if the cat has runny eyes and nose, he will suspect herpes or calicivirus, he will inspect the ulcers, the location, size and make a guarded assessment.

He may wish to perform some tests such as:

  • Urinalysis to check kidney function.
  • CT scan and biopsy to diagnose cancer.
  • Biopsy.

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