Mouth ulcers: when should you worry?

Most mouth ulcers are harmless and heal on their own within one to two weeks. You should have one checked by a dentist or doctor if it lasts longer than three weeks, keeps getting bigger, bleeds, feels hard or oddly painless, comes with fever or swallowing problems, or keeps returning without an obvious cause.

What is a mouth ulcer?

A mouth ulcer is a small, painful sore inside the mouth where the thin lining has broken down. It is usually round or oval, white or yellowish in the centre with a red border, and appears on the inside of the cheeks or lips, on or under the tongue, or on the gums.

The most common type is the aphthous ulcer, often called a canker sore. Doctors usually describe three forms:

• Minor ulcers: the most common, usually smaller than 1 cm, healing within about one to two weeks without a scar.
• Major ulcers: larger, deeper and more painful; they can take several weeks to heal and sometimes leave a scar.
• Herpetiform ulcers: a rare form made of clusters of pinpoint sores.

Common causes and triggers

Often there is no single clear cause. Common triggers include:

• accidentally biting your cheek or tongue, or a burn from very hot food;
• a sharp or broken tooth, a rough filling, or dentures or braces that rub;
• brushing too hard, or a toothbrush with hard bristles;
• stress, tiredness and feeling run down;
• hormonal changes, for example around a period or during pregnancy;
• low levels of iron, vitamin B12 or folic acid;
• some medicines, and stopping smoking;
• in some people, toothpastes containing sodium lauryl sulphate (SLS), a foaming agent.

Ulcers that keep returning, or many at once, are sometimes linked to a general health condition such as coeliac disease or Crohn’s disease, which is one reason they deserve a proper check.

How long should a mouth ulcer last?

A typical minor ulcer is most painful for the first few days, then slowly improves and in most cases heals completely within one to two weeks.

A useful rule, used by health services such as the NHS guide to mouth ulcers, is the three-week rule: any ulcer that has not healed after three weeks should be examined by a dentist or doctor. This does not mean that something serious is happening.

Warning signs: when should you worry?

Book an examination without waiting if you notice any of the following:

• an ulcer that has not healed after three weeks;
• an ulcer that keeps getting larger, or is larger than usual;
• a sore that feels hard, raised or lumpy, or that is surprisingly painless;
• a white or red patch in the mouth that does not rub off;
• bleeding, numbness, or a tooth near the sore that becomes loose without a clear reason;
• ulcers with fever, feeling generally unwell, difficulty swallowing or swollen glands in the neck;
• ulcers that come back very often, or many at once.

Rarely, a long-lasting ulcer can be an early sign of mouth cancer. The risk is higher in people who smoke cigarettes or narghile (waterpipe), use chewing tobacco, or drink alcohol regularly. Problems found early are usually simpler to treat, so a calm, timely check is more useful than worrying at home.

What happens when the dentist checks an ulcer

Examining a mouth ulcer is simple, painless and usually part of a normal consultation:

1. Questions: how long the ulcer has been there, whether you have had others, your general health, your medicines, smoking and diet.
2. Examination: the dentist looks at the ulcer and the rest of the mouth, tongue, gums and neck, and checks for a sharp tooth, rough filling or denture that may be rubbing.
3. Treating the cause: if a sharp edge is found, it can often be smoothed, or a denture adjusted, so the area can heal.
4. Review: if the cause is not clear, the dentist may ask to see you again after one to two weeks to make sure the ulcer is healing.
5. Further tests if needed: if an ulcer does not heal or looks unusual, you may be referred for blood tests through your doctor or for a biopsy, which means removing a small sample of tissue under local anaesthesia so it can be examined under a microscope.

The cost depends on what is needed, such as a simple examination, X-rays, smoothing a tooth, adjusting a denture or review visits, and is explained during your consultation before anything is done.

Relief and care while an ulcer heals

There is no instant cure for an ordinary ulcer, but you can ease the pain and help it heal:

• rinse with warm salt water a few times a day;
• use a soft toothbrush and keep brushing gently, even near the sore;
• avoid spicy, salty, acidic and very hot foods and drinks until it settles;
• drink through a straw if drinking is painful;
• ask a pharmacist about a numbing gel, a protective paste or an antiseptic mouthwash suitable for you.

Do not put aspirin tablets directly on an ulcer or on the gums, as this can burn the lining of the mouth. If ulcers are severe or very frequent, a dentist or doctor may prescribe a stronger treatment.

Preventing mouth ulcers from coming back

Not every ulcer can be prevented, but a healthy mouth makes them less likely and easier to spot. Regular check-ups and preventive care such as scaling and polishing allow sharp teeth, worn fillings and ill-fitting dentures to be noticed early. Healthy gums matter too: read about the early signs of gum disease and how it is treated.

A sore that does not heal can also come with an unpleasant taste or smell; our article on the real causes of bad breath explains what to look out for. Women who are expecting may notice changes in their gums and mouth; see which dental care is safe during pregnancy. If you smoke, stopping is one of the most helpful steps for the long-term health of your mouth.

Mouth ulcer checks at Ajam Dental Clinic in Tripoli

At Ajam Dental Clinic, the dentists can examine a persistent or recurring mouth ulcer during a consultation and explain calmly what should happen next. Dr. Soumaya Ajam holds a University Diploma in Oral Pathology from Université Saint-Joseph de Beyrouth, a field that covers mouth lesions and ulcers. Ulcers and sores in babies, children and teenagers are handled by Dr. Soumaya Ajam, whose specialty is paediatric dentistry.

Patients come to our clinic on Fouad Chehab Boulevard, Al-Makateb Building, 1st Floor, from across Tripoli — Zahriyeh, Al-Tall, Dam wa Farez, Azmi Street, Bahsas and Beddawi — as well as from the rest of North Lebanon. If you have an ulcer that has lasted more than three weeks or simply worries you, contact us to book a consultation by phone or WhatsApp.

This article provides general information for patients. It does not replace an examination by a dentist, who can advise you on your own situation.