With leukoplakia (loo-koh-PLAY-key-uh), thickened, white patches form on your gums, the insides of your cheeks, the bottom of your mouth and, sometimes, your tongue. These patches can't be scraped off.
Doctors don't know what causes leukoplakia but consider tobacco — whether smoked, dipped or chewed — to be the main culprit in its development.
Leukoplakia usually isn't dangerous, but it can sometimes be serious. Although most leukoplakia patches are noncancerous (benign), some show early signs of cancer. Many cancers on the floor of the mouth — beneath the tongue — occur next to areas of leukoplakia. For that reason, it's best to see your dentist if you have unusual, persistent changes in your mouth.