Leukoplakia is a condition in which thick, hard, white patches form inside the mouth and cannot be wiped off. Leukoplakia is commonly caused by irritation, such as from the rubbing of a rough tooth or a poorly fitting denture, or from smoking or using smokeless tobacco.

Leukoplakia may clear up if the source of the irritation is removed, by fixing the tooth or denture, or by stopping tobacco use. It may take several weeks or even months for the leukoplakia to go away completely.

In some cases, leukoplakia can be an early sign of cancer of the mouth.