Canker sore on mouth
A canker sore is a painful shallow ulcer inside the mouth; gentle care helps, but a persistent or unusual sore needs examination.
The short answer
A canker sore is a small, shallow ulcer on the non-keratinized lining inside the mouth, often with a pale center and a red border, and it is not the same as a cold sore. It can make eating, brushing, or speaking uncomfortable.
Where in the mouth can canker sores commonly appear?
Canker sores commonly affect the inner lip, cheek, soft palate, or tongue. Local trauma, stress, illness, nutritional problems, hormonal changes, or an immune-related condition may be associated with them, but one sore may have no clear trigger.
How can you make eating and brushing more comfortable?
Use a soft brush, choose cool soft foods, and avoid spicy, acidic, or rough foods that touch the ulcer. A dentist can recommend a protective or anti-inflammatory mouth treatment after checking the lesion and your medical history.
When should a canker sore in the mouth be checked?
Arrange an examination if the ulcer is unusually large, very painful, recurrent, accompanied by fever or several other sores, or does not heal as expected. Urgent care is needed if mouth pain or swelling interferes with drinking or breathing.
How can a dentist confirm what a mouth sore is?
Ask whether the sore has the typical location and appearance of a canker sore or whether trauma, infection, medication, or another condition is more likely. Ask which topical treatment can protect it and whether recurrent episodes need further evaluation.
Frequently asked questions
Are canker sores contagious?
Typical aphthous ulcers are not spread like cold sores, but an examination is useful when the appearance is unusual.
Can toothpaste irritate a canker sore?
Some ingredients or strong flavors may aggravate sensitive tissue, so use a mild product and avoid scrubbing the ulcer.
Who wrote this page
This library is published by Dental Nation, a licensed dental group practising in the United Arab Emirates. Pages are written and overseen by the same clinical team that treats patients in our clinics, and are held to a fixed editorial standard for safety and accuracy.
This page is patient education, not medical advice, and cannot replace an examination. Anything urgent — facial swelling, trauma, uncontrolled bleeding or severe pain — needs a dentist or emergency care now.