What is a Mouth Ulcer?

A mouth ulcer or canker sore is a painful open sore inside the mouth caused by a break in the mucous membrane. The condition is also called aphthous stomatitis or aphthous ulcer, especially if there are multiple or recurring sores. Ulcers are generally 3-5mm diameter but can develop to the area of your little finger's nail (1cm+)

They are most common on the inner cheek, inner lip, tongue, soft palate, floor of the mouth, and occasionally found at the back of the throat.