Canker sore inside the mouth
A canker sore is a shallow, painful ulcer on movable mouth lining that usually heals without a dental procedure.
The short answer
A canker sore is a small ulcer of the oral mucosa, often with a pale centre and red border, that can hurt while eating or speaking. It usually affects non-keratinised lining such as the inner lip, cheek, or underside of the tongue.
What is the direct answer?
What does this question mean?
A minor injury, stress, illness, hormonal change, or nutritional problem may precede an ulcer, although the exact trigger is often unclear. A cold sore is different because it typically begins as grouped blisters on the lip edge.
What can you do next?
Rinse gently with salt water, choose soft cool foods, and avoid spicy, acidic, or rough foods while the ulcer heals. A pharmacist or dentist can recommend a topical treatment when pain interferes with eating.
When should you seek dental care?
Arrange an examination if an ulcer is unusually large, recurrent, spreading, associated with fever, or not healing. A persistent or firm ulcer needs assessment to exclude trauma, infection, immune disease, or another oral lesion.
What should you ask the dentist?
Ask whether the lesion is a canker sore, traumatic ulcer, cold sore, or another condition, and whether a sharp tooth or appliance is rubbing it. Ask what treatment can reduce pain and how recurrence should be evaluated.
Frequently asked questions
Is a canker sore contagious?
A canker sore is not spread by ordinary contact, unlike an active cold sore caused by herpes viruses.
Can a sharp tooth cause a mouth ulcer?
Yes. Repeated rubbing from a tooth, filling, denture, or appliance can produce a traumatic ulcer that needs removal of the irritant.