What causes a mouth sore that does not heal?

A mouth sore that does not heal may be caused by trauma, infection, irritation, treatment effects, or an underlying mouth condition. Mouth cancer, tongue cancer, and oral leukoplakia can present with a persistent sore or patch, but a sore alone does not establish cancer.

Sores can follow a bite, sharp tooth, denture rubbing, burn, viral infection, tobacco exposure, dry mouth, or a medicine that affects the mouth. Pay attention to its exact site, appearance, pain, bleeding, change in size, and whether there is a white or red patch, neck lump, numbness, loose tooth, or difficulty chewing, swallowing, or moving the tongue. These details help a clinician decide whether examination, dental care, swab testing, or a biopsy is needed.

Arrange an examination with a dentist or clinician when a sore does not heal, keeps returning, or has no clear injury. Check for a sharp tooth, broken filling, or denture pressure, but do not repeatedly irritate the area while investigating it. Use a soft toothbrush, avoid tobacco and alcohol, choose softer foods if chewing hurts, and keep the mouth clean. People receiving chemotherapy, radiotherapy, or other cancer treatment should contact their care team before using mouth products or remedies.

Seek urgent help if swelling makes breathing or swallowing difficult, bleeding does not settle, pain is severe, or you cannot drink enough to stay hydrated. Prompt assessment is needed for a growing sore, persistent bleeding, a neck lump, numbness, or new difficulty speaking, chewing, or swallowing.

Could a tooth, denture, infection, medicine, or treatment be irritating this area? Does the sore need a swab, dental treatment, specialist review, or biopsy? What mouth care is suitable for me?