Mouth sores and inflammation

[Michiko]

Mouth sores and inflammation vary in appearance and size and can affect any part of the mouth, including the lips (see Lip Sores and Inflammation).
People may have swelling and redness of the lining of the mouth or individual, painful ulcers. An ulcer is a sore that forms a hole in the lining of the mouth when the top layer of cells breaks down. Many ulcers appear red, but some are white because of dead cells and food debris inside the center portion. Blisters are sores that are raised and filled with clear fluid (they are called vesicles or bullae, depending on size). Rarely, the mouth looks normal even though people have symptoms of mouth inflammation (burning mouth syndrome).
Noncancerous (benign) ulcers are usually painful until healing is well under way. The pain makes eating difficult, which sometimes leads to dehydration and undernutrition. Some sores go away but recur.