Aphthous Ulcer (Canker Sores)

Aphthous ulcer is a kind of mouth ulcer that is non-infectious but tends to recur. It is commonly present on the tongue and oral mucosa of the cheeks, lips and throat.

Photograph showing the position of an aphthous ulcer on the oral mucosa near the upper front teeth.
Photograph showing the position of an aphthous ulcer on the tongue.
Photograph showing the position of a small round aphthous ulcer on the lip.


Photograph showing the presence of aphthous ulcer on the lip that is yellowish with a reddish margin.

Aphthous ulcer begins with a localised swelling of the affected oral mucosa to form a small round or oval shaped blister. After a day, the blister bursts and becomes a whitish or yellowish ulcer with a red margin. When irritated by spicy, salty or sour food with strong taste, pain will be felt and saliva secretion will be increased.

Causes of aphthous ulcer

To date, the aetiology of aphthous ulcer has not been confirmed. However, the predisposing factors are known as follows:

  • Oral tissue trauma.
  • Stress.
  • Problem in endocrine system, i.e. hormonal disturbance.
  • Immune system disorder.
  • Gut problems.
  • Malnutrition (especially the deficiency of vitamin B12, folic acid, iron, etc.).
  • Wearing an unfit denture.


Aphthous ulcer usually heals within 7 to 14 days. If the situation persists for more than 3 weeks or there is recurrent formation of new aphthous ulcers, you should consult a doctor for a body check-up to see if other treatments are necessary. If it is because of wearing an unfit denture, you should consult your dentist to adjust the denture. When necessary, a new denture may have to be made.

To avoid the pain from getting aggravated, you should:

  • Avoid touching the area when toothbrushing.
  • Avoid eating hard, coarse, hot or spicy food.
  • Apply ointment prescribed by the doctor or dentist onto the area to relief pain.

Method to prevent recurrent aphthous ulcer

Since the aetiology of aphthous ulcer has not been confirmed, the only way to prevent recurrence is by eliminating the predisposing factors.