Mouth ulcers
Mouth ulcers are small, painful sores inside the mouth. They are very common, are not contagious, and usually heal by themselves within 1 to 2 weeks. Most are minor, but an ulcer that does not heal needs to be checked.
- Usually heal
- Within 1 to 2 weeks
- Contagious
- No
- Get checked
- If an ulcer lasts more than 3 weeks
What they look like
- Round or oval sores, usually white or yellow in the middle, with a red edge
- Found on the inside of the cheeks, lips or tongue, or under the tongue
- Painful, especially when eating, drinking or brushing your teeth
- Sometimes there is a tingling or burning feeling before the ulcer appears
Common causes
- Biting the inside of your cheek or tongue, or rubbing from braces, dentures or a sharp tooth
- Burning your mouth on hot food or drink
- Stress, tiredness and hormonal changes
- Toothpaste or mouthwash that contains sodium lauryl sulfate, in some people
- Not enough iron, vitamin B12 or folate in the diet
- Some medicines, and some health conditions such as coeliac disease or inflammatory bowel disease
What you can do yourself
- Avoid spicy, salty, acidic (such as citrus fruits) and very hot food and drinks while it is sore. Cool, soft foods are more comfortable.
- Use a soft toothbrush, and try a toothpaste without sodium lauryl sulfate.
- Rinse gently with warm salty water.
- Drinking through a straw can help you avoid touching the ulcer.
- Ask us about pharmacy treatments, including numbing gels, sprays and lozenges, antiseptic mouthwashes, and corticosteroid lozenges or pastes that can help ulcers heal faster.
How PRX Pharmacy can help
Our pharmacists can recommend a suitable treatment to ease the pain and speed healing. Some gels are not suitable for children, or for people with certain conditions or medicines, so please tell us who it is for.
When to get medical help
Call 999 or go to A&E if:
- • Your face, lips or tongue are swelling, or you have difficulty breathing or swallowing
Contact your GP practice or call 111 the same day if:
- • An ulcer has lasted more than 3 weeks, or is not getting better
- • You have ulcers that keep coming back, or many at once
- • An ulcer is unusually large, or is painless and has hard or raised edges
- • You have a red or white patch, or a lump, in your mouth or on your tongue
- • You have difficulty swallowing or speaking, or unexplained bleeding from the mouth
- • You have ulcers together with a fever, a rash, eye or genital sores, or diarrhoea or weight loss
- • You smoke or drink a lot of alcohol and have a mouth ulcer that does not heal
If you are ever worried and unsure, ask us or call 111. Trust your instincts — it is always better to ask.
This guide is general information written by the PRX Pharmacy team. It does not replace advice from a pharmacist or doctor who knows your medical history.
Last updated 24 September 2026. Clinically reviewed by Milan Patel, Pharmacist on 24 September 2026.
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