What causes a white film in your mouth?
Photo Credit: Courtesy of 3DStockPhoto (your mouth image)
The white patches are usually harmless. But in rare cases, leukoplakia can develop into oral cancer. Oral lichen planus: With this condition, a problem with your immune system causes white patches to form in your mouth and on your tongue. ... Oral thrush: This is an infection of the mouth caused by Candida yeast.