Mouth ulcers

Mouth ulcers are common and should clear up on their own within a week or 2. But see a GP or dentist if you have a mouth ulcer that lasts longer than 3 weeks.

How you can treat mouth ulcers yourself

Mouth ulcers are rarely a sign of anything serious, but may be uncomfortable to live with.

They need time to heal and there's no quick fix.

Avoiding things that irritate your mouth ulcer should help:


  • use a soft-bristled toothbrush

  • drink cool drinks through a straw

  • eat softer foods

  • get regular dental check-ups

  • eat a healthy, balanced diet


  • do not eat very spicy, salty or acidic food

  • do not eat rough, crunchy food, such as toast or crisps

  • do not drink very hot or acidic drinks, such as fruit juice

  • do not use toothpaste containing sodium lauryl sulphate

A pharmacist can help with mouth ulcers

A pharmacist can recommend a treatment to speed up healing, prevent infection or reduce pain, such as:

You can buy these without a prescription.

How to rinse with salt mouthwash
  1. Dissolve half a teaspoon of salt in a glass of warm water – warm water helps salt dissolve.
  2. Rinse your mouth with the solution, then spit it out – do not swallow it.
  3. Repeat as often as you like.

Non-urgent advice: See a dentist or GP if your mouth ulcer:

  • lasts longer than 3 weeks
  • is different to other mouth ulcers you've had before, for example if it's bigger than usual or near the back of your throat
  • bleeds or becomes more painful and red – this may be a sign of an infection

Although most mouth ulcers are harmless, a long-lasting mouth ulcer is sometimes a sign of mouth cancer. It's best to get it checked.

You should also see a GP if you have other symptoms such as:

  • ulcers anywhere else on your body, such as your skin or genitals
  • painful, red or swollen joints

Treatment from a dentist or GP

A GP or dentist may prescribe stronger medicine to treat severe, persistent or infected mouth ulcers.

Possible treatments include:

Check if you have a mouth ulcer

A large, white, circular mouth ulcer on the inside of the bottom lip.
Mouth ulcers usually appear inside the mouth on the cheeks or lips.
A large, white, circular mouth ulcer on the underside of the tongue.
Ulcers can also appear on the tongue.

You may have more than 1 ulcer at a time.

Mouth ulcers are not contagious and should not be confused with cold sores.

Cold sores appear on the lips or around the mouth and often begin with a tingling, itching or burning sensation. They can also appear as a small group of pinhead-sized ulcers inside the mouth.

Causes of mouth ulcers

Most single mouth ulcers are caused by things you can try to avoid, such as:

Sometimes they're triggered by things you cannot always control, such as:

If you have several mouth ulcers, it can be a symptom of:

Page last reviewed: 11 March 2024
Next review due: 11 March 2027