Mouth ulcer

Author: A/Prof Amanda Oakley, Dermatologist, Hamilton, New Zealand, January 2016.

What is a mouth ulcer?

Mouth ulcers are common. They are one form of stomatitis. A mouth ulcer is damaged epithelium and its underlying lamina propria. Mouth ulcers may be due to trauma, irritation, radiation, infections, drugs, inflammatory disorders and unknown causes.

The most common presentation of mouth ulcers is with painful, recurrent aphthous stomatitis, also known as aphthosis, aphthae, aphthous ulceration and canker sores.

Patients may present to doctors or to dentists with a mouth ulcer for assessment and treatment. They can also have cutaneous and systemic symptoms and signs.

Mouth ulcers

Who gets mouth ulcer and how are mouth ulcers classified?

Males and females of all ages and races experience mouth ulcers.

Acute and recurrent infection

Acute single-episode ulceration

Recurrent/multiple ulcers

Chronic mouth ulcer

Differential diagnosis includes other inflammatory disorders in which there is no true ulceration, such as migratory glossitis/geographic tongue.

What causes aphthous mouth ulcer?

The cause or causes of aphthous mouth ulcers are not well understood. Current thinking is that the immune system is disturbed by some external factor and reacts abnormally against a protein in mucosal tissue. 

Although most people with aphthous stomatitis are healthy, it may relate to:

  • Genetic factors; a strong family history of aphthous stomatitis is common
  • Other illness, lack of sleep, being “run down”, psychogenic stress
  • Trauma from inadvertent bite or brushing teeth

In some patients, there are additional predisposing factors.

What are the clinical features of mouth ulcer?

A patient with mouth ulcer should be questioned and examined with a differential diagnosis in mind. Consider:

  • Is the ulcer solitary or are there multiple ulcers?
  • What part or parts of the mouth are involved?
  • Is the patient feeling well or unwell?
  • Is this a single episode, or have the ulcers occurred before?
  • Does the patient have any underlying condition or disease?
  • Does anyone else close to the patient have similar symptoms?

Recurrent aphthous ulceration

  • One or many lesions scattered throughout the mouth
  • Round or ovoid in shape
  • Surrounded by erythematous halo
  • Punched-out yellow-grey centre
  • Painful, especially on eating or drinking.

Recurrent aphthous ulcers are divided into 3 types.

  • Minor recurrent aphthous ulceration: lesions are under 10 mm in diameter and heal within 10–14 days.
  • Major recurrent aphthous ulceration (much less common); coalescent or large ulcers with raised margins > 10 mm in diameter that take longer to heal; often associated with fever, dysphagia, malaise.
  • Herpetiform recurrent aphthous ulceration: this is is uncommon, and is characterised by crops of numerous grouped 1–3 mm ulcers on or under the tongue.

Complications of mouth ulcer

Most mouth ulcers heal without problem. Consider biopsy of a non-healing ulcer.

How are mouth ulcers diagnosed?

Mouth ulcers are usually easy to diagnose. Occasionally biopsy is performed, particularly if considering cancer. It should be taken from the indurated edge of an inflammatory ulcer or from an inflamed but non-ulcerated site.

If the patient has frequent, prolonged or large ulcers, or is unwell, the following tests may be done to assess general and gastrointestinal health.

Selected patients may undergo further assessment including endoscopy if there is suspicion of inflammatory bowel disease.

If specific toothpaste or food is thought to precipitate ulcers, allergy tests including prick tests, patch tests and specific IgE testing may be performed. The results can be difficult to interpret.

What is the treatment for mouth ulcer?

General measures

Symptomatic relief may be obtained from:

  • Avoidance of hard, spicy, salty or acid food
  • Avoidance of toothpaste containing sodium lauryl/laureth sulfate
  • Antiseptic, anti-inflammatory and analgesic mouthwash or spray
  • Pain relief and local treatment

Local therapy

Nicotine-containing gum has been reported to be effective, but it is not recommended because it’s highly addictive and has many adverse effects (see smoking).

Systemic therapy

Systemic therapy is intended to reduce frequency of ulceration. A Cochrane review (2012) of systemic treatments for recurrent aphthous stomatitis was inconclusive. The following are reported to be useful in at least some patients.

Mouth ulcers are not preventable in all patients. Some people can reduce the number and severity of their ulcers by ensuring plenty of rest and avoiding known triggers.

What is the outlook for mouth ulcers?

The outlook depends on the type of mouth ulcers and their cause, if known.

There is a gradual tendency for recurrent aphthous stomatitis to become less severe in later life.


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