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Mouth sores (mouth ulcers)
Most mouth ulcers are harmless and heal on their own in 1 to 2 weeks. A sore that lasts longer needs checking.
This is general information, not a diagnosis. It does not replace a check by a dentist or doctor. If you are worried, contact a dental professional.
What helps
- Use a soft toothbrush.
- Eat softer food. Drink cool drinks with a straw.
- Avoid spicy, salty, sour or crunchy food, and very hot drinks.
- A pharmacist can suggest a gel, spray or mouthwash.
When to see a dentist
- A mouth ulcer lasts longer than 3 weeks.
- It is not like ulcers you have had before, for example bigger, or near the back of your throat.
- It bleeds, or gets more painful and red.
- You also have ulcers on other parts of your body, or sore, swollen joints (see a doctor).
Most ulcers are not serious. But a mouth ulcer that does not heal can sometimes be a sign of mouth cancer. That is why a sore lasting over 3 weeks should be checked by a dentist or doctor.
Related: Oral health basics
Sources
Paraphrased in plain words. Links checked and accessed 21 Oct 2026.
- NHS (UK). “Mouth ulcers”. https://www.nhs.uk/conditions/mouth-ulcers/ (accessed 21 Oct 2026).
- World Health Organization. “Oral health – fact sheet”. https://www.who.int/news-room/fact-sheets/detail/oral-health (accessed 21 Oct 2026).