Mouth Ulcers
Key facts
Mouth ulcers are common and usually clear up on their own within a week or 2. They are rarely a sign of anything serious, but see a GP or dentist if one lasts longer than 3 weeks.
Most often affects:People who are tired, stressed or anxiousPeople who have recently stopped smokingDuring pregnancyPeople with braces, dentures or a sharp tooth
What commonly causes mouth ulcers
- Biting the inside of your cheek
- Badly fitting dentures, braces, rough fillings or a sharp tooth
- Cuts or burns while eating or drinking — hard food or hot drinks
- A food intolerance or allergy
- Damaging your gums with a toothbrush, or an irritating toothpaste
- Feeling tired, stressed or anxious
- Hormonal changes, such as during pregnancy, and your genes — some families get them more often
- A vitamin deficiency, such as iron, zinc, folic acid, vitamin B or vitamin D
- Some medicines, including some NSAIDs, beta blockers or nicorandil
- Several ulcers at once can be a symptom of another condition, such as hand, foot and mouth disease, oral lichen planus, Crohn's disease or coeliac disease
What helps at home
- Use a soft-bristled toothbrush
- Drink cool drinks through a straw, and eat softer foods
- Avoid very spicy, salty or acidic food, and rough, crunchy food such as toast or crisps
- Avoid very hot or acidic drinks, such as fruit juice
- Avoid toothpaste containing sodium lauryl sulphate
- Rinse with a salt mouthwash: dissolve half a teaspoon of salt in a glass of warm water, rinse, and spit it out — do not swallow it
- A pharmacist can recommend an antimicrobial mouthwash, a painkilling gel or spray, or corticosteroid lozenges, without a prescription
When to get help
These three levels are different. Getting the level right is the single most useful thing this page can do for you.
Non-urgent advice: see a GP if
- The ulcer lasts longer than 3 weeks — most are harmless, but a long-lasting mouth ulcer is sometimes a sign of mouth cancer, so it is best to get it checked (a dentist or GP)
- It is different to ulcers you have had before — bigger than usual, or near the back of your throat
- It bleeds, or becomes more painful and red — this may be a sign of infection
- You also have ulcers anywhere else on your body, such as your skin or genitals
- You also have painful, red or swollen joints
What to do next
Not sure whether mouth ulcers needs a doctor? These are your options, cheapest and fastest first.
Questions people ask about mouth ulcers
Reducing the chance of it coming back
- Get regular dental check-ups — a sharp tooth or rough filling can keep causing ulcers
- Eat a healthy, balanced diet
- Use a soft-bristled toothbrush, and a toothpaste without sodium lauryl sulphate if ulcers keep coming back
Conditions this can be part of
Listed alphabetically, not by likelihood — this page does not tell you which one you have.
- Coeliac disease
- Cold sores
- Crohn's disease
- Hand, foot and mouth disease
- Oral lichen planus
Sources and further reading
This page was written from the following published guidance. All links checked 26 August 2026.
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