Mouth ulcers are small, painful sores that appear inside the mouth.

They are usually red, yellow, or white, with a red edge.

Most mouth ulcers are harmless and heal on their own, but some may need checking.

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What causes mouth ulcers?

The most common cause is minor damage, such as:

• Biting your cheek or tongue.
• A sharp tooth or rough filling.
• Sharp food.
• Toothbrushing too hard.
• Poorly fitting dentures or dental appliances.

These are called traumatic ulcers.

They are usually single ulcers and heal once the cause is removed.

Recurrent aphthous ulcers (aphthous stomatitis)

Some people get mouth ulcers repeatedly, even when they are otherwise healthy. This is known as recurrent aphthous stomatitis.

• The exact cause is not known.
• It is not infectious.
• It is not usually inherited.

This type is most common in children, teenagers, and young adults.

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Types of recurrent mouth ulcers

Minor ulcers

These are the most common type.

• Usually appear on the cheeks, lips, tongue, or gums.
• About the size of the tip of a pencil.
• May appear in small clusters.
• Usually heal within 1 to 2 weeks.

Major ulcers

These are less common but more severe.

• Larger and deeper than minor ulcers.
• Often very painful, especially when swallowing.
• Can appear near the tonsils.
• May take several weeks to heal.
• Any ulcer lasting longer than 3 weeks should be checked.

Multiple small ulcers

Very rarely, people may develop many tiny ulcers at once.

• Can number dozens at a time.
• Usually heal within 1 to 2 weeks.

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Less common causes of mouth ulcers

In some cases, mouth ulcers may be linked to:

• Viral infections, such as herpes simplex (more common in children).
• Anaemia or vitamin deficiencies.
• Certain blood conditions.
• Digestive or skin conditions.
• Problems with the immune system.

Sometimes, mouth ulcers can be the first sign of another health condition.

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Are mouth ulcers contagious?

No. Mouth ulcers cannot be passed on by kissing or sharing cups, cutlery, or food.

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How are mouth ulcers treated?

Treatment depends on the cause.

• Sharp teeth or rough fillings may be smoothed.
• Dentures may need adjusting.
• Mouthwashes or gels may help reduce pain and inflammation.
• In some cases, tablets or prescription treatments may be needed.

Your dental or medical team will advise what is best for you.

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Can mouth ulcers be prevented?

You may be able to reduce the risk by:

• Keeping your mouth clean and healthy.
• Using a soft, good-quality toothbrush.
• Avoiding foods that irritate your mouth if ulcers are present.
• Eating a balanced diet with plenty of fruit and vegetables.

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When should I be concerned?

Most mouth ulcers heal on their own.

You should seek advice if:

• An ulcer lasts longer than 3 weeks.
• Ulcers keep coming back.
• You feel unwell or have other symptoms.
• The ulcer is very painful or getting worse.

If you are unsure, it is always best to have mouth ulcers checked by your dentist or doctor.

Learn more about mouth ulcers and mouth cancer on our dedicated page.