Mouth ulcers in dogs: stomatitis and other causes

Overview

Stomatitis means inflammation of the oral lining. It may affect the gums, inner cheeks, tongue or back of the mouth, for example. Ulcer appearance alone cannot reliably establish the cause. Local dental disease or systemic disease can cause similar injuries.

CCUS causes painful oral ulcers, often where the lining contacts teeth. However, not every contact lesion beside a tooth is CCUS. Lymphocytes and plasma cells in a biopsy of chronic inflammation are non-specific findings.

Yeast-related stomatitis is rare in dogs. It too can cause ulcers on the tongue or other oral surfaces.

Causes

Local injury and dental disease

Sharp plant material or a lodged foreign body can injure the lining. Thread wrapped beneath the tongue may be missed without careful examination. Chemicals and electrical burns can cause inflammation and ulcers. Chewing a Dieffenbachia houseplant can also irritate the mouth.

Periodontal disease can cause a contact lesion on the opposing lining. In CCUS, an exaggerated local immune response to dental plaque antigens is suspected. The precise mechanism is unknown. CCUS differs from an autoimmune blistering disease caused by autoantibodies.

Cheek or sublingual tissue may become trapped between teeth during chewing and sustain repeated injury.

Other oral disease, prolonged antibiotics or reduced immunity may predispose dogs to yeast infection.

Kidneys, the immune system and tumours

Advanced kidney disease can involve uraemic oral ulcers. In pemphigus vulgaris, the immune system attacks structures holding epithelial cells together. Fragile blisters can rupture rapidly and appear only as ulcers at examination. Erythema multiforme can also involve severe stomatitis.

Eosinophilic oral lesions are suspected to relate to hypersensitivity, for example to food or environmental irritants. A tumour can ulcerate and bleed. Oral lymphoma can sometimes appear as widespread ulceration rather than a single lump.

Risk factors

Risk factors depend on the cause. Chronic ulcerative stomatitis has been found in Maltese, Miniature Schnauzers and Labrador Retrievers, for example. These observations cannot establish a general breed or sex predisposition covering every oral ulcer.

In a study of 42 dogs with chronic stomatitis, ages ranged from 1.9–15.5 years, averaging 9.4 years. Small dogs were common, with a median weight of 5.4 kilograms. Eosinophilic stomatitis, in contrast, often appears young, usually before 3 years old. It has been described in Cavalier King Charles Spaniels and Siberian Huskies, for example. Medication can trigger erythema multiforme.

Males have been described as more predisposed than females to eosinophilic stomatitis. This observation concerns that rare inflammatory form and is not applied to other mouth ulcers.

Typical symptoms

Severity depends on inflammation location and extent.

• Your dog drools more than usual.
• Breath smells unpleasant.
• Saliva may contain blood.
• Appetite decreases or eating becomes difficult.
• Your dog paws at the mouth or resists opening it.
• Pain causes lip smacking.
• Your dog may lose weight.

Contact lesions often appear inside the lip or cheek opposite the upper canine and upper carnassial tooth. The tongue's side can also ulcerate against teeth. In the 42-dog chronic stomatitis study, more than 60% also had lesions beyond usual contact sites.

The reported distribution of eosinophilic oral lesions involved the palate in 65.4% of cases. The tongue was affected in 26.9%. Other oral sites accounted for 7.7%. This distribution concerns eosinophilic stomatitis rather than all mouth ulcers.

Complications and consequences

Impaired eating and swallowing can cause malnutrition. Difficulty drinking can predispose dogs to dehydration. Severe pain can prevent appropriate oral home care. Even small amounts of residual plaque can sustain CCUS inflammation. Ulcers can develop after every tooth is removed because plaque also forms on other oral surfaces.

In a study of 42 dogs with chronic lymphoplasmacytic stomatitis, 81% achieved complete resolution of signs after different treatment stages. This concerns that inflammatory group rather than every ulcer cause. Fungal stomatitis has a poor outlook if its predisposing disease cannot be controlled. Pemphigus vulgaris can be life-threatening through loss of the epithelial barrier. The outlook for a tumour-related ulcer depends on tumour type and spread.

Diagnosis at the vet

Examination covers the whole mouth

History includes onset, medicines and possible chemical or foreign body exposure. Thorough assessment of teeth, periodontal pockets, tongue and other oral surfaces often requires anaesthesia. Dental X-rays assess periodontal tissues and jawbone. Ulcer locations are compared with nearby teeth and radiographic findings. Changes in other skin, lip margins or pads may guide investigation towards immune-mediated disease.

Biopsy distinguishes similar-looking diseases

Biopsy helps distinguish CCUS, eosinophilic inflammation, autoimmune blistering diseases and tumours. Lymphocytes and plasma cells alone do not establish the cause. Persistent or unusual lesions may also need more detailed imaging.

Oral lesions have been reported in more than 90% of dogs with pemphigus vulgaris. Only the mouth was affected in 6% of these dogs. Pemphigus foliaceus, in contrast, almost exclusively causes skin lesions. The name pemphigus alone therefore does not establish which oral disease is suspected.

Around 30% of dogs with erythema multiforme may have oral lesions. Kidney dysfunction is investigated through blood tests and other tests guided by findings. Blood eosinophils are increased in 33–60% of eosinophilic stomatitis patients. A normal blood cell count therefore does not exclude an eosinophilic oral lesion.

Oral bleeding alone does not always mean lining ulceration. Clotting disorders can appear as mucosal bleeding. Assessment therefore distinguishes actual tissue injury, bleeding and concurrent systemic signs.

Treatment

Treating a local cause

Your vet prescribes medication and procedures according to diagnosis. Material lodged in the tongue or other tissue is removed. Extensive burns may require dead tissue removal. Pain relief forms part of care for severely affected dogs. Dehydration is corrected with fluids when needed. Soft food can make a painful mouth easier to use. Prolonged inadequate eating may require a feeding tube.

If soft tissue continually becomes trapped between teeth, excess tissue can be removed surgically to prevent further injury.

Plaque control and dental treatment

Contact lesion treatment includes cleaning teeth and treating periodontitis. Severely damaged teeth may be removed. Teeth contacting an ulcer may also need removing even if otherwise healthy. Removing every tooth is not the first treatment for every chronic mouth ulcer.

In the 42-dog study, 62% achieved complete resolution primarily through periodontal treatment. Seventeen per cent became entirely toothless because of ulcerative mucosal disease. These results support staged planning according to dental findings and response.

Your vet may supplement plaque control with a topical chlorhexidine product.

Immune-mediated and systemic causes

CCUS treatment may also include anti-inflammatory and immunosuppressive medication. With eosinophilic stomatitis, possible contributions from food and chewing materials are assessed. Your vet may prescribe a glucocorticoid or another immunosuppressive medicine when needed. Such a granuloma has been described as resolving within 10–20 days of treatment starting. This interval does not apply to every oral ulcer.

With a kidney-related ulcer, renal dysfunction is treated too. Tumour treatment is planned from biopsy results. Antibiotics may be needed for bacterial infection, but do not replace treatment of the cause.

A hydrolysed diet may be selected for a suspected food reaction. Yeast infection treatment addresses both the predisposing disease and the fungal infection itself.

Prevention

Regular plaque removal through brushing reduces dental disease-related inflammation. Home care does not remove the need for professional oral examinations. Avoid very hard chewing objects because they can fracture teeth.

Oral checks also look for lumps, ulcers and abrasions. Preventing chewing of electrical cables and corrosive substances prevents associated local injuries. Dental home care alone cannot prevent every autoimmune or systemic disease-related oral ulcer.

Home care remains necessary after professional dental treatment because cleaned teeth can be maintained at home.

Important for dog owners

Record food intake, drinking, drooling and bloody saliva. Report new medicines, dietary changes and objects chewed. Bring previous dental treatment records and X-rays if available. Do not force open a severely painful mouth.

Agree the need for soft food and pain relief before leaving. Ask separately when brushing can resume and how to give prescribed medicines with a painful mouth. Arrange follow-up and a plan if eating is impossible. Also watch for skin, lip and pad changes. New breathing difficulty, severe bleeding or collapse requires emergency care.

Frequently asked questions

Do mouth ulcers always mean poor dental care?

Plaque and periodontitis can relate to contact lesions, but ulcers have other causes too. Kidney disease or an autoimmune blistering disease can damage the lining, for example. The cause is therefore investigated by examining the whole mouth and taking a biopsy when needed, rather than limiting care to cleaning alone.

Must every tooth be removed?

Decisions depend on dental findings and how inflammation responds to initial treatment. Many dogs with chronic inflammatory stomatitis benefit from periodontal treatment without full-mouth extraction. Some also need more extensive extractions or immunosuppressive medication. Ulcers can sometimes persist even in a toothless mouth.

Can a mouth ulcer indicate a tumour?

An oral tumour can ulcerate and bleed. It may also cause drooling, unpleasant smell or difficulty eating. Biopsy helps distinguish a tumour from inflammation. Persistent or unusual lesions particularly need investigation because their appearance can resemble other lining diseases.

How quickly does a mouth ulcer heal?

Healing speed depends on the cause. An eosinophilic granuloma has been described as resolving within 10–20 days of treatment starting. CCUS may instead persist or recur after dental treatment. The figure therefore is not a shared healing time for every cause.

Can I brush teeth when there are mouth ulcers?

Plaque reduction forms part of contact lesion and CCUS treatment. However, ulcer pain can make brushing and oral medication difficult. Home care is therefore planned individually alongside pain relief and any dental procedures, without forcibly handling a painful mouth.