Mouth ulcer

Mouth ulcers are painful sores that appear in the mouth. They’re uncomfortable but they’re usually harmless. Most clear up by themselves within 1 to 2 weeks.

Mouth ulcers are common and can usually be managed at home, without seeing your dentist or GP.

What does a mouth ulcer look like?

Mouth ulcers are usually round or oval sores that commonly appear inside the mouth on the:

  • cheeks
  • lips
  • tongue

They can be white, red, yellow or grey in colour and swollen.

You may have more than one mouth ulcer at a time and they may spread or grow.

Mouth ulcers shouldn’t be confused with cold sores, which are small blisters that develop on the lips or around the mouth. Cold sores often begin with a tingling, itching or burning sensation around your mouth.

When to get help

Speak to a pharmacist if:

  • you have a mouth ulcer

They can give you advice and treatment.

If you have a dental problem you should always phone your dentist first. If you’re not registered with any dental practice then you should read our advice on dental emergencies.

Your pharmacist may advise that you see your GP or dentist if:

  • your mouth ulcer has lasted 3 weeks
  • you keep getting mouth ulcers
  • the mouth ulcer grows bigger than usual or is near the back of your throat
  • your mouth ulcer becomes more painful or red – this could be a sign of a bacterial infection, which may need treatment with antibiotics

Mouth ulcers are also a possible symptom of hand, foot and mouth disease. Speak to your GP or phone 111 if you’re unsure.

How to treat mouth ulcers

Most mouth ulcers clear up by themselves within 1 to 2 weeks without treatment.

However, treatment can help to reduce swelling and ease any discomfort. This may help if you keep getting mouth ulcers or your mouth ulcer affects eating and drinking.

Self care

There are things you can do to speed up healing.


  • use a soft toothbrush to brush your teeth
  • drink cool drinks through a straw
  • eat softer foods
  • get regular dental check-ups
  • eat a healthy, balanced diet
  • try to reduce stress and anxiety


  • 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 chewing gum
  • do not use toothpaste containing sodium lauryl sulphate

Pharmacy medicines

You can get several types of mouth ulcer treatment from a pharmacy. Speak to your pharmacist about the best treatment for you.

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:

  • steroid mouth spray or steroid tablets that dissolve in your mouth
  • painkilling gels, ointments, sprays or tablets
  • mouthwashes to kill or remove any germs in your mouth

What causes mouth ulcers?

In many cases, the reason for mouth ulcers is unclear. Most single mouth ulcers are caused by damage to the lining inside of the mouth. For example:

  • accidentally biting the inside of your cheek or a sharp tooth
  • poorly fitting dentures
  • hard food
  • a faulty filling

It’s not always clear what causes mouth ulcers that keep returning, but triggers are thought to include:

  • stress and anxiety
  • hormonal changes – some women develop mouth ulcers during their monthly period
  • eating certain foods – such as chocolate, spicy foods, coffee, peanuts, almonds, strawberries, cheese, tomatoes and wheat flour
  • toothpaste containing sodium lauryl sulphate
  • stopping smoking – when you first stop smoking, you may develop mouth ulcers

Your genes are also thought to have a role. Around 40% of people who keep getting mouth ulcers report that it runs in their family.

Medical conditions

Mouth ulcers can sometimes be caused by certain medical conditions, such as:

Medications and treatments

Mouth ulcers can sometimes be caused by certain medications or treatments, such as:

  • non-steroidal anti-inflammatory drugs (NSAIDs) – such as ibuprofen
  • nicorandil – a medication sometimes used to treat angina
  • beta-blockers – used to treat conditions such as angina, high blood pressure and abnormal heart rhythms
  • a side effect of chemotherapy or radiotherapy – this is known as mucositis

Is it mouth cancer?

In a few cases, a long-lasting mouth ulcer can be a sign of mouth cancer. If mouth cancer is detected early, the chances of a complete recovery are good. Regular dental check-ups are the best way to detect the early signs.

Last updated:
23 March 2023

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