Cat Mouth Ulcers: 5 Causes, Told by Position

Mouth ulcers in cats come from 5 different problems, and the position of the sore is the fastest way to separate them. Chronic gingivostomatitis (FCGS) sits behind the last molars, calicivirus ulcers sit on the tongue and hard palate, uremic ulcers sit under the tongue tip, a foreign body lodges between the upper premolars, and an eosinophilic granuloma appears on the lip or the palate. Age, breath and whether the cat still eats narrow that list before a single test is run.

A cat that drops food after 1 or 2 chews, tilts its head while eating, or trails a 5 cm string of saliva is in pain now. Book a dental exam within 48 hours instead of watching for 2 weeks to see whether it settles.

Match the sore's position to the cause

Position is the most useful finding on the first exam. Open the mouth gently under good light and look at 4 zones: inside the lips, the sides of the tongue, under the tongue, and the back of the mouth behind the molars. Photograph each zone once a week so change is measurable rather than remembered. Ulcers that cross the midline and involve the gum line behind the molars point at FCGS; single ulcers on the tongue point at calicivirus or trauma.

Cause	Usual site	Typical age (years)	Lesion size (mm)	First test
FCGS	Gum line behind molars	4 to 10	3 to 15	Full-mouth X-ray
Calicivirus	Tongue, hard palate	0.3 to 3	2 to 10	History plus PCR swab
Uremic ulcer	Under the tongue tip	8 to 16	1 to 5	BUN, creatinine, SDMA
Foreign body	Between upper premolars	0.5 to 6	5 to 25	Probe under sedation
Eosinophilic granuloma	Upper lip, palate	2 to 8	2 to 20	Cytology or 8-week diet trial

FCGS: full-mouth X-rays on day one

FCGS is an immune reaction to plaque that affects roughly 0.7 to 4 percent of cats and is seen most often from 4 years old. Full-mouth extraction resolves or greatly improves about 60 to 80 percent of cases; 10 to 20 percent need 1 to 3 surgeries because roots fracture, and 20 to 40 percent still need long-term medication. Tooth resorption runs alongside it in 20 to 60 percent of adult cats and is invisible without films, so a full-mouth series of 8 to 10 intraoral views matters more than the visual exam. That series takes 10 to 15 minutes under sedation and costs roughly 150 to 300 dollars.

Pain control drives whether the cat eats: buprenorphine 0.01 to 0.02 mg per kg every 6 to 8 hours, gabapentin 5 to 10 mg per kg every 8 to 12 hours, meloxicam 0.1 mg per kg once then 0.05 mg per kg, and 0.12 percent chlorhexidine gel once daily. Refractory cases are sometimes trialed on ciclosporin at 5 mg per kg once daily for 4 to 6 weeks. Full details of the surgical pathway sit in the stomatitis guide.

Calicivirus: ulcers that close in 7 to 14 days

Feline calicivirus incubates 3 to 5 days, gives a fever of 39.5 to 40.5 C, and leaves 2 to 10 mm ulcers on the tongue and hard palate, often with sneezing and eye discharge in the same week. Support means warm food at 37 C, 5 to 10 ml of water by syringe every 2 hours for a cat that refuses to drink, and the same pain protocol as above. Most ulcers heal in 7 to 14 days. Carriers shed virus for 30 days and some for life, so isolate a new cat for 21 days.

Uremic ulcers: read the bloodwork before the mouth

Tiny 1 to 5 mm ulcers under the tongue tip or on the lingual frenulum, combined with ammonia breath and a cat over 8 that has lost 5 to 10 percent of body weight, point at kidney failure rather than infection. BUN is often above 100 mg per dL and creatinine above 5 mg per dL at this stage. Antibiotics do nothing here; the mouth improves when the kidneys are supported with 30 to 50 ml per kg per day of fluids, a phosphate binder, and a rinse 2 to 3 times daily. The vet decides the fluid plan, never a home guess.

Foreign body and eosinophilic granuloma

A bone shard, sewing needle, grass awn or thread under the tongue produces one-sided drooling within 12 to 24 hours, pawing at the face and refusal of hard food. It needs sedation, a blunt probe and 2 radiographic views; never pull a thread that is wrapped under the tongue. Eosinophilic granuloma is a raised pink plaque of 2 to 20 mm on the upper lip or palate, confirmed by eosinophils on cytology; an 8 to 12 week hydrolyzed or novel-protein diet clears many cases, and a 6 mm punch biopsy is the next step if nothing changes in 4 weeks. If the cat may have chewed a plant or household product, check the toxicity list before assuming infection.

3 signs that localize the pain

Watch one meal. Food dropped after 2 chews means premolar pain at the back of the mouth. Head tilt to 1 side during chewing means a one-sided lesion. Swallowing soft food without chewing, or lapping liquid only, means the tongue base or the area under it. Drool tells a second story: thin and clear suggests nausea, thick and blood-tinged suggests ulceration. Weight is the slow signal, and a 5 percent loss in 30 days means intake has already dropped.

When X-rays and biopsy are due

Full-mouth films under anesthesia are due at the first dental exam if ulcers persist past 14 days, if any tooth is mobile, or if the cat is over 6 years old. Biopsy is due for a single mass over 5 mm that has not shrunk in 21 days, for any one-sided lesion, and for tissue that bleeds at a light touch. Squamous cell carcinoma under the tongue in a cat aged 10 to 12 often presents as a firm 5 to 30 mm mass, and a delay of 2 to 4 weeks can remove the surgical option. Signs that overlap with tumor presentation are collected in the oral tumor guide.

What to do in the next 24 hours

• Photograph the mouth in 4 zones tonight and note the size in mm next to a ruler.
• Offer 3 small meals of warm wet food at 37 C instead of 1 large bowl.
• Weigh the cat today; a 4 kg cat that drops to 3.8 kg has lost 5 percent.
• Book a dental exam within 48 hours if the cat is drooling or dropping food.
• Skip human pain gels and antiseptic sprays; several are toxic to cats.

Frequently asked