A mouth ulcer that has not healed within two weeks should be checked, although most ulcers are harmless and heal on their own. Arrange a dental or medical appointment if it persists, keeps returning, or worsens. Seek earlier review for a lump, red or white patch, bleeding, numbness, or trouble swallowing. A lasting sore does not automatically mean cancer, but it needs checking.
How long should a mouth ulcer take to heal?
Most ordinary mouth ulcers heal within one to two weeks. Common canker sores, which develop on the soft tissues inside the mouth, usually improve without specific treatment. Their typical appearance includes a round or oval sore with a pale centre and a reddish border. The discomfort often settles as the tissue heals.
According to Mayo Clinic, a sore lasting two weeks or longer is a reason to consult a healthcare professional. This is particularly important if the ulcer is not getting smaller, repeatedly breaks open, or appears to be worsening instead of healing. An appointment allows a dentist or doctor to assess whether irritation, infection, or another underlying problem could be responsible.
Why might a mouth ulcer refuse to heal?
A persistent mouth ulcer can have several explanations. Sometimes, the original sore is repeatedly irritated before it has time to heal. In other cases, an infection, a medicine, or an underlying health condition may contribute to the problem.
MedlinePlus identifies several possible causes of mouth sores, including local injuries, medication reactions, infections, nutritional deficiencies, and conditions affecting the immune system. Depending on the circumstances, a healthcare professional may consider the following possibilities:
- Repeated injury: Accidentally biting the cheek or tongue, brushing too forcefully, or rubbing against a sharp tooth can damage the lining of the mouth. Braces and poorly fitting dentures may also cause irritation.
- Irritating foods or oral-care products: Spicy, acidic, or rough foods can aggravate an existing ulcer. Certain toothpaste ingredients or mouth-care products may also contribute to irritation in some people.
- Recurrent canker sores: Some people develop new ulcers before older ones have healed. Frequent or unusually large sores deserve assessment, especially when the usual healing pattern changes.
- Infections: Certain viral, fungal, or bacterial infections can cause sores or other changes inside the mouth.
- Medicines or medical conditions: Some medicines can cause mouth sores. Nutritional deficiencies, including low levels of vitamin B12 or folate, and certain inflammatory or immune-related conditions may also be associated with ulcers.
The location of a sore, how long it has been present, whether it is painful, and whether similar ulcers have occurred before can all help guide an assessment. Removing an obvious source of friction may help an injury heal, but a persistent ulcer should still be examined rather than assumed to be the result of minor trauma.
Which warning signs mean a mouth ulcer needs attention?
The length of time an ulcer lasts is important, but other changes can also affect how quickly it should be assessed. The National Institute of Dental and Craniofacial Research (NIDCR) advises seeing a dentist or doctor for certain possible signs of oral cancer that persist for more than two weeks. These findings do not establish a diagnosis, but they should not be ignored.
- An ulcer that persists: A sore that remains for two weeks, does not show signs of healing, or keeps returning before previous sores resolve.
- A red or white patch: A persistent change in the colour or appearance of the lining of the mouth.
- A lump or thickened area: An unusual change in the tissue of the mouth, lips, or throat, or a lump in the neck.
- Bleeding or numbness: Unexplained bleeding from the affected area or a change in sensation in the tongue or other parts of the mouth.
- Problems with normal mouth movements: Difficulty chewing, swallowing, speaking, moving the tongue, or opening the jaw comfortably.
Arrange an assessment sooner rather than waiting for the two-week mark if the sore is rapidly worsening, unusually large, or associated with significant pain or difficulty eating and drinking. Seek urgent medical help if you have difficulty breathing or cannot swallow fluids. People with a weakened immune system should also contact their healthcare professional promptly about persistent or worsening mouth sores.
Does a mouth ulcer that will not heal mean cancer?
No. Many persistent mouth sores have non-cancerous explanations, including repeated injury, inflammatory conditions, and infections. However, oral cancer can sometimes appear as a persistent ulcer or as a red or white patch. It is not possible to distinguish every harmless sore from a concerning lesion by appearance alone.
Cleveland Clinic explains that mouth ulcers have many possible causes and that a sore lasting three weeks or longer should be evaluated. It is sensible to arrange a check earlier if an ulcer has not healed within two weeks, particularly if its appearance is unusual or it comes with other warning signs.
Some factors increase the risk of oral cancer, including tobacco use and heavy alcohol consumption. The risk also increases with age, and oral cancers occur more often in adults over 40. These factors help clinicians assess the overall picture, but their presence or absence cannot determine the cause of an individual ulcer. A persistent sore warrants attention even in someone who has never used tobacco or alcohol.
What happens when a dentist or doctor examines a persistent ulcer?
The assessment usually begins with questions about when the ulcer appeared, whether it has changed, whether similar sores have occurred before, and whether eating or swallowing has become difficult. The clinician may also ask about medicines, recent dental treatment, tobacco and alcohol use, and other health conditions that could be relevant.
The mouth will be examined for the ulcer's location, size, shape, edges, and surrounding tissue. The dentist or doctor may also check nearby teeth and dental appliances for sources of repeated irritation and examine the neck for unusual lumps. These findings are considered alongside the person's medical history and the course of the symptoms.
If the cause is unclear, further tests may be appropriate. Depending on the findings, these can include blood tests to investigate possible underlying conditions or a biopsy, in which a small tissue sample is examined. A biopsy is not needed for every mouth ulcer; the decision depends on the appearance and persistence of the lesion and the clinician's assessment.
What can you do while waiting for an appointment?
Simple measures may reduce irritation and make eating or drinking more comfortable, although they should not delay an examination of a persistent sore.
- Use a soft-bristled toothbrush and clean your teeth gently.
- Choose soft foods and cool drinks if chewing or swallowing is uncomfortable.
- Avoid foods that aggravate the area, including very spicy, salty, acidic, hot, or crunchy foods.
- Drink enough fluids to stay hydrated.
- Check for a possible source of repeated injury, such as a sharp tooth or poorly fitting dental appliance, and arrange dental care if needed.
- Ask a pharmacist, dentist, or doctor about suitable pain relief or an oral treatment if discomfort is affecting daily activities.
The NHS guidance on mouth ulcers also recommends gentle oral hygiene and avoiding foods and drinks that irritate the sore. Avoid scraping, cutting, or attempting to burn an ulcer away, as this may cause further injury. Do not start supplements or prescription treatments simply because an ulcer is taking longer than expected to heal; treatment should match the underlying cause when one is identified.
When should you book an appointment?
If your mouth ulcer has lasted two weeks without healing, arrange an appointment with a dentist or doctor rather than continuing to wait for it to disappear. Seek assessment sooner if the sore is worsening, repeatedly returning, bleeding without an obvious cause, or accompanied by a lump, persistent red or white patches, numbness, or difficulty swallowing.
Most mouth ulcers are not caused by cancer, but a persistent sore is worth investigating. An examination can identify a treatable source of irritation, help determine whether further tests are needed, and reduce the risk of overlooking a more serious cause.