A persistent or unusual ulcer should not be ignored.
Most ulcers settle relatively quickly
Mouth ulcers commonly heal within one or two weeks. A sore area may be irritated by biting, a sharp tooth or a rough filling, among other causes. Looking at an ulcer yourself cannot reliably establish why it is there or whether it needs treatment.
Use duration as a prompt
Have an ulcer checked by a dentist or doctor if it lasts more than three weeks. An ulcer that is unusually large, in an unusual place, bleeds or becomes more painful and red should also be assessed. Do not keep putting off an examination because the area only hurts occasionally.
Describe what has changed
Note when the ulcer first appeared, whether it has changed and whether anything rubs against it. Tell the clinician about any additional symptoms. Booking a dental assessment does not imply a particular diagnosis or a need for an X-ray; the clinician decides which investigations, if any, are relevant.
Read the sources
General educational information. It is not a diagnosis or a personalised treatment plan. No clinician approval is claimed.
NHS: Mouth ulcersPrepared 2026-09-20 · Sources accessed 2026-09-20
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