Symptom Definition

Mouth ulcers and sores vary in appearance and size and can affect any part of the mouth, including the lips. People may experience swelling and redness of the mouth lining or painful ulcers. An ulcer is a sore that forms a hole in the lining of the mouth when the surface layer of cells breaks off. Many ulcers appear red, but some are white because of dead cells and food debris on the inside of the central part. Blisters are raised sores filled with clear fluid. Rarely, the mouth looks normal, although people may have symptoms of oral inflammation (burning mouth syndrome).