An ulcer that comes back is different from one that never heals
A small ulcer that heals and returns later follows a different course from a single sore that stays in one place. To distinguish them, your clinician will ask when it began and whether it ever healed completely in between. Photographs can help you describe how it has changed.[3]
Some mouth ulcers have a relatively clear cause, such as biting your cheek. Others involve several factors or are difficult to distinguish by appearance alone. Even if this sore feels familiar, do not assume its cause must be the same as before.[3]
A rough tooth may keep irritating the same spot
Common causes include accidentally biting the cheek, a sharp tooth, a rough filling or a denture that rubs against the mouth lining. Repeated contact with the same spot can make healing more difficult.[1][3]
If your tongue detects a rough edge, or eating always rubs the same area, point it out at your appointment. Do not file down a tooth or restoration yourself. A clinician can check whether the contact point corresponds to the sore, then monitor whether it heals after the irritation is addressed.[3]
Why do some sources say two weeks and others three?
The NHS advises that ordinary mouth ulcers usually heal within one to two weeks and should be assessed by a dentist or doctor if they last longer than three weeks. The US National Institute of Dental and Craniofacial Research recommends having sores, irritation, or red or white patches checked if they persist for more than two weeks.[1][2]
These are not deadlines at which a condition suddenly changes. A practical approach is to book an assessment if a sore remains unchanged after two weeks without signs of healing, and seek care sooner if it is getting worse. There is no need to wait deliberately for a time limit you found online.[1][2]
Being advised to have it checked does not mean it is cancer
Persistent sores deserve attention because they have many possible causes. A non-healing sore being listed in oral cancer guidance does not mean that every lingering ulcer is cancer. Do, however, mention any accompanying lump, red or white patch, change in sensation or difficulty swallowing.[2]
Your clinician will examine the mouth and surrounding tissues before deciding whether further tests are needed. An expert consensus on difficult oral ulcers suggests considering a biopsy when the history and examination do not explain a lesion that has persisted for more than two weeks. This does not mean every ulcer needs an immediate biopsy; it describes a possible next step when the cause remains unclear.[3]
Reduce irritation and keep track of changes
While your mouth is sore, use a soft toothbrush and temporarily avoid foods that irritate it, including spicy, acidic, rough-textured or very hot foods. A pharmacist or clinician can advise on pain relief. Temporary relief, however, is not a reason to skip an assessment of a persistent sore.[1]
Note when it started, how it has changed, any recently used medicines and other recurring symptoms. Nutritional deficiencies or an underlying health condition sometimes need investigation, but not everyone needs the same tests or supplements. The key is to consider the visible sore alongside your daily habits and medical history.[3]
Research and institutional sources
- NHS. Mouth ulcers.View source ↗NHS guidance on typical healing times and self-care for mouth ulcers.
- National Institute of Dental and Craniofacial Research. Oral Cancer.View source ↗NIDCR advice on having persistent changes in the mouth assessed.
- Zeng X, et al. Difficult and complicated oral ulceration: an expert consensus guideline for diagnosis. Int J Oral Sci. 2022;14:28. doi:10.1038/s41368-022-00178-0.View source ↗Expert consensus guidance on the assessment of persistent oral ulcers with an unclear cause.
Bracketed numbers in the text link to these sources. This article provides general health information; individual diagnosis and treatment plans are determined after a clinical consultation.
