SYMPTOM
Mouth ulcers
Owners may observe mouth ulcers in their pet, which can present in various ways depending on the underlying cause.
Immune-mediated
Conditions in which the immune system targets the tissues of the mouth can produce ulceration, often affecting the gums, tongue, or palate. These patterns may appear as part of a broader immune response or remain confined to the oral cavity.
Infectious
Viral, bacterial, or fungal infections can damage the oral mucosa, leading to ulcers that may be single or multiple. The pattern often depends on the organism involved and the animal's immune response.
Metabolic
Kidney disease and certain other metabolic disturbances can lead to ulceration of the mouth, typically through the accumulation of waste products that irritate the oral tissues. These ulcers often appear alongside other systemic signs.
Traumatic or chemical
Physical injury from chewing hard objects, electrical burns, or contact with caustic substances can produce focal ulcers. The distribution and appearance tend to reflect the nature and site of the initial insult.
Neoplastic
Tumours arising in the mouth may ulcerate as they grow, creating lesions that can bleed or appear irregular. These tend to be localised initially but may change in character over time.
Dental
Severe dental disease, including advanced periodontal disease or tooth root abscesses, can lead to ulceration of adjacent soft tissues. The ulcers often sit near the affected tooth or along the gum line.
Why timing matters
Early observation
When mouth ulcers are first noticed, they may represent a recent injury, an acute infection, or the early stage of a systemic process. The animal's behaviour around food and water, the location of the ulcer, and whether there are other signs can all contribute to the picture at this stage. In some cases, early ulcers resolve as the underlying trigger is removed or as healing progresses.
Later presentation
Ulcers that persist beyond a few weeks, recur after apparent healing, or increase in size may reflect an ongoing process rather than a self-limiting event. Chronic ulceration can accompany systemic illness, immune-mediated disease, or progressive conditions such as neoplasia. The surrounding tissue—whether inflamed, thickened, or bleeding—often adds further context to the evolving picture.
Some ulcers remain stable in size and appearance, whilst others change over days to weeks. Healing tends to occur within one to two weeks for simple traumatic ulcers, whereas those linked to systemic or immune-mediated causes may wax and wane or fail to heal without addressing the underlying process. Individual variation in healing capacity, concurrent disease, and the nature of the cause all influence the trajectory.
Conditions commonly associated
Feline Calicivirus
Calicivirus characteristically causes ulceration of the tongue, gums, and palate.
Feline Herpesvirus (FHV-1)
Feline herpesvirus can cause ulceration of the oral mucosa, particularly affecting the tongue and gums, as part of the inflammatory response to active viral replication in the tissues lining the mouth. These ulcers typically appear alongside other signs of upper respiratory infection.
Chronic Kidney Disease in Cats
In cats with chronic kidney disease, mouth ulcers can develop when waste products accumulate in the bloodstream and irritate the oral mucosa, a phenomenon sometimes referred to as uraemic stomatitis. These ulcers tend to appear in more advanced stages of the disease.
Acute Kidney Injury
Acute kidney injury can lead to mouth ulcers through a similar mechanism to chronic disease—accumulated toxins in the blood irritate and damage the delicate lining of the mouth. This oral involvement may become apparent as kidney function declines rapidly.
Dental Disease in Cats
Dental disease in cats can produce ulceration where inflamed or infected oral tissues come into contact with tooth surfaces, or where the immune response to bacterial plaque causes breakdown of the gingival margin. In some cases, tooth resorption or stomatitis may contribute to ulcer formation in the mouth.
When to explore further
Ulcers that have been present for more than two to three weeks without signs of healing may warrant closer attention, particularly if they are changing in size or appearance.
If the ulcers are accompanied by reduced appetite, difficulty eating, drooling, or weight loss, these changes may indicate that the process is affecting the animal's ability to take in food or reflects a broader systemic picture.
Multiple ulcers appearing simultaneously, or ulcers recurring after apparent resolution, can suggest an underlying condition rather than a single isolated event.
If there is bleeding from the ulcer, swelling of the surrounding tissue, or an unpleasant odour, these features may reflect infection, advanced dental disease, or tissue breakdown.
When other signs are present—such as increased thirst, lethargy, vomiting, or changes in behaviour—these observations can help place the oral findings in a wider context.
Mouth ulcers gain meaning when considered alongside the animal's broader health picture, including appetite, behaviour, and any other changes that have emerged over the same period. Documenting the appearance, location, and duration of the ulcers can be a useful reference point in conversations about the animal's wellbeing. The trajectory over the following days to weeks—whether the ulcers are healing, stable, or changing—often informs how the picture is understood and what may be explored further.
Last reviewed: 24 April 2026 · Dr Alastair Greenway MRCVS