Stomatitis in dogs:ulcers on the cheeks, strong breath odour and what to do about it

What stomatitis in dogs is, and what CUPS is

Stomatitis is a general term for inflammation of the mouth lining: the cheeks, lips, palate and tongue. It has many causes, and treatment depends on the cause. So “stomatitis” is not yet a diagnosis but a description of what we see.

Chronic ulcerative paradental stomatitis (CUPS) is a specific condition. “Paradental” means “next to the teeth”: the ulcers form where the lining lies against the tooth surfaces. Newer sources also call it canine chronic ulcerative stomatitis (CCUS).

The lining of the mouth in these dogs is thought to over-react to the bacteria in dental plaque (the soft bacterial film on the teeth): an amount of plaque that another dog lives with for years without ulcers causes deep, painful inflammation in them. The exact mechanism is still being studied. As far as we know, CUPS does not pass from dog to dog, but it does not go away on its own either: while there is plaque on the teeth, the ulcers usually come back.

The oral mucosa is part of the mouth’s protective barrier, and stomatitis breaks it down. I explain how this barrier works in How a dog’s and cat’s mouth works.

What stomatitis in a dog looks like

If you gently pull the lip back, with CUPS you can see ulcers or bright red patches on the inside of the lip or cheek — directly opposite a tooth. Most often they lie against the upper canines and the large upper cheek teeth the dog uses to crack hard things (the fourth premolars), because the cheek rests most tightly against them. Because of this mirror-image pattern they are also called contact ulcers.

• the ulcers are pale grey, yellowish or whitish with a red rim and bleed when touched;
• the tooth opposite carries plaque or tartar;
• the edges of the tongue can be affected too if they touch the teeth;
• the gums are sometimes less inflamed than the cheek lining — this sets CUPS apart from ordinary gingivitis;
• the saliva is thick and stringy, and the fur around the mouth is wet or stained.

Only look when your dog is calm, and do not force it: the ulcers are very painful, and even a gentle dog may snap. If your dog allows it, take a photo from the side with the lip lifted — it will help at the consultation.

Symptoms: what owners notice

CUPS hurts all the time, and especially during meals. Owners most often notice:

• very strong bad breath that does not go away;
• thick, stringy saliva, sometimes with blood, and a wet chin;
• the dog comes to the bowl but eats carefully, drops hard pieces and picks soft food;
• pawing at the face, head shaking, not letting anyone touch the lips;
• not allowing a look inside the mouth, or growling, when it used to allow it;
• playing less with toys, losing weight, becoming lethargic.

Some dogs keep eating and only change the way they eat, so a good appetite does not mean the pain is mild. I describe other signs of mouth pain in Signs of tooth pain in dogs.

Not every ulcer is CUPS: when a biopsy is needed

Ulcers in a dog’s mouth can have quite different causes, and some of them are serious. Conditions that can look similar include:

• autoimmune diseases of the skin and mucous membranes — pemphigus, pemphigoid and lupus, in which the immune system attacks the body’s own tissues;
• tumours, including malignant ones such as squamous cell carcinoma and lymphoma, which in the mouth can look like ulcerated inflammation;
• kidney disease — in severe kidney failure ulcers can appear on the mouth lining and the breath may smell of ammonia (more in Breath that smells of acetone, urine or fish);
• burns — chemical (household cleaning products) or electrical, when a dog chews a cable;
• injuries and foreign objects — stick splinters, sharp bone fragments, or a tooth pressing into the lining because of a faulty bite.

So I take a biopsy — a small piece of tissue examined under a microscope (histology) — if the ulcers are not where the lining touches the teeth, are one-sided, look atypical, sit next to a growth, or do not heal once the plaque has been removed. Only histology shows what the process is. When clinically indicated I add blood tests, including kidney function. More on biopsy of growths in the mouth in A growth on the gums in a dog or cat.

How the diagnosis is made

At the examination and consultation I assess where the ulcers are, how they relate to the teeth, how much plaque there is, how the dog eats and whether it is losing weight. This is often enough to suspect CUPS. But a painful mouth cannot be examined fully without anaesthesia.

Under general anaesthesia I examine the whole mouth, probe every tooth and take full-mouth dental radiographs: dogs with CUPS often have periodontal disease as well, and diseased teeth keep the inflammation going. If needed, I take a biopsy at the same time. Before anaesthesia the dog needs blood tests and, when clinically indicated, other checks — I tailor them to each dog.

How stomatitis in dogs is treated

The aim is to remove what the mouth lining reacts to — plaque — and to stop it building up again. I make the plan individually, and it depends on whether daily tooth care is possible for your dog.

Whether teeth can be kept is something we decide together. If your dog lets you brush every day and you are ready to keep it up, some teeth can sometimes stay under strict plaque control. But brushing hurts at first and missed days quickly bring the ulcers back, so for many dogs the most reliable relief comes from extracting the teeth the lining touches.

Dogs adapt well to life without some or even all of their teeth: after healing they eat soft and softened food, and many manage kibble too. I explain when extraction is justified in When a dog needs a tooth extracted.

1. 01

   Pain relief and preparation

   After the examination and consultation I prescribe pain relief if needed, so the dog can eat until the procedure, and plan the pre-anaesthetic checks.

2. 02

   Professional clean under anaesthesia

   COHAT: cleaning above and below the gum line, polishing, dental radiography and, if needed, a biopsy.

3. 03

   Extractions

   I extract teeth with periodontal disease and often those the ulcers touch; in severe cases most or all of the teeth. Follow-up X-rays confirm that the roots have been removed completely.

4. 04

   Daily plaque control

   Once healed, gentle daily brushing of the remaining teeth with a pet toothpaste, plus the products I recommend. Without this, plaque returns within days.

5. 05

   Follow-up checks

   We assess healing and any remaining inflammation; if it persists, we discuss the next steps.

Can stomatitis in dogs be cured with medicines

Anti-inflammatory and immunomodulating medicines (those that damp down an excessive immune reaction), pain relief and, when clinically indicated, antibiotics can ease the condition. Only a vet should prescribe them, and they are useful as a bridge to the procedure or as an add-on afterwards if inflammation persists. But medicines do not remove plaque, so once they are stopped the ulcers usually return.

Long-term steroid use has side effects, and repeated courses of antibiotics without a plan encourage resistant bacteria. Gels, sprays and rinses do not replace treatment — I explain why in Why ointments, gels and sprays do not treat teeth. Anaesthesia-free teeth cleaning will not help either: it does not remove plaque below the gums and is very painful for a dog with ulcers.

What to expect after treatment

The mouth lining needs time to heal, so I judge the result at follow-up checks rather than in the first few days. After plaque and diseased teeth have been dealt with, many dogs feel much better: the strong odour fades, they eat more willingly and let you stroke their face again.

At the same time, CUPS is a chronic condition. If teeth have been kept, plaque must be removed from them every day, and if the ulcers come back we review the plan. That is why I do not promise a cure “once and for all” but explain what you can realistically expect for your dog. How stomatitis behaves in cats and how it differs is covered in Stomatitis in cats.

How much treating stomatitis in a dog costs

The cost is made up of the examination and consultation, pre-anaesthetic checks, anaesthesia, a professional clean under the COHAT protocol and the surgical stage. The number of extractions and the need for a biopsy only become clear after the examination under anaesthesia and the X-rays, so that is when I give the exact figure.

Frequently asked questions