Mouth and jaw guide

5 min read

Mouth ulcers

Mouth ulcers are common, but ulcers lasting more than three weeks, recurring often or linked with worrying symptoms should be assessed.

Mouth ulcers are sore areas inside the mouth. Many short-lived ulcers are linked with minor trauma, stress, certain foods, braces, dentures or unknown triggers.

This guide does not diagnose the cause of an ulcer. An ulcer lasting more than three weeks, recurring frequently or looking unusual should be assessed by a dentist or GP.

At a glance

Common pattern

Short-lived sores

Many mouth ulcers are sore but settle without specific dental treatment.
Avoid triggers that rub or sting the area.
Keep the mouth clean while the area heals.

Assessment signs

More than three weeks

See a dentist or GP if an ulcer lasts more than three weeks.
Seek advice for recurrent, very painful or unusual-looking ulcers.
Check dentures, braces or sharp teeth if they keep rubbing the same area.

Urgent concerns

Prompt help

Urgent advice is needed if ulcers appear with severe swelling, fever or difficulty swallowing.
Use emergency medical care for breathing difficulty or rapidly spreading swelling.
A serious injury inside the mouth needs urgent assessment.

Contents

Mouth ulcers are common but need review if persistent

A short-lived mouth ulcer is often not serious, but persistence beyond three weeks, frequent recurrence or unusual features need professional assessment.

Possible causes or contributing factors

Accidental biting, sharp teeth, rough fillings, braces or dentures.
Stress, some foods, toothpaste irritation or unknown triggers.
Dry mouth, medical conditions, nutritional factors or medicine effects.
Infection or wider health problems in some cases.

What you can do now

Avoid spicy, sharp or acidic foods if they sting.
Keep teeth and dentures clean and avoid rubbing the ulcer.
Arrange assessment if the ulcer lasts more than three weeks.

What not to do

Do not ignore an ulcer that persists beyond three weeks.
Do not repeatedly traumatise the area with sharp foods or appliances.
Do not use strong chemicals or home remedies on the ulcer.

When to contact a dentist

An ulcer is caused by a sharp tooth, filling, denture or brace.
An ulcer lasts more than three weeks or keeps returning.
You have mouth pain that affects eating or drinking.

When urgent dental care is needed

Severe mouth pain is linked with swelling, fever or a bad taste.
A dental appliance has caused a deep sore or bleeding area.
There is facial swelling or difficulty opening the mouth.

When to call 999 or go to A&E

What a dentist or relevant professional may assess or do

Assess the ulcer, teeth, dentures, braces and soft tissues.
Smooth or adjust irritating dental factors where appropriate.
Refer or advise GP assessment if the ulcer pattern needs wider review.

Frequently asked questions

When should a mouth ulcer be checked?

NHS guidance says to see a GP or dentist if a mouth ulcer lasts longer than three weeks.

Can a sharp tooth cause an ulcer?

Yes. Sharp edges, braces or dentures can rub the mouth. A dentist can assess and adjust the cause where appropriate.

Are mouth ulcers contagious?

Common mouth ulcers are not usually contagious, but other mouth infections can look different and may need assessment.

Need mouth ulcer guidance?

Browse Odenta mouth and jaw guidance and arrange dental or GP assessment for persistent or concerning ulcers.

Browse mouth and jaw guides

Official sources

These links open external official guidance pages for further help.

Content reviewed by Dr Majid Saeed · 13 July 2026

References used for this guide are listed above.

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