What Causes a White Coating on the Tongue?

A white coating on the tongue may indicate a variety conditions, ranging in severity from a simple dental hygiene issue to a precancerous growth. An overgrowth of yeast is a leading cause of a white coating on the tongue. If you develop a white coating on the tongue, see your doctor to determine the cause and best course of action.

White substances on your tongue may be a sign of an underlying problem. (Image: ARENA Creative/iStock/Getty Images)

Thrush

The mouth normally hosts yeast and many types of bacteria. A white film on the tongue can be caused by an overgrowth of naturally occurring yeast, a condition known as oral thrush. Although there are many types of fungi that can be found in the mouth, a June 2013 article in the "Science Journal of Clinical Medicine" notes that the most common cause of oral thrush is Candida albicans. One characteristic of thrush is that the white coating can be easily rubbed off the tongue, typically revealing a reddened area that may bleed. Taking antibiotics or inhaled steroids increases the risk for oral thrush.

Oral Leukoplakia

Oral leukoplakia describes a white patch in the mouth that may involve the tongue or other areas. The patches may be small or involve nearly the entire surface of the tongue. Unlike the white coating caused by thrush, leukoplakia patches cannot be rubbed off. Chronic irritation of the mouth by tobacco use and heavy alcohol consumption increase the risk for oral leukoplakia. Men tend to be affected more than women. Because these patches may transform into cancer, it is important to have them evaluated by a doctor.

Smoking and Dehydration

Two other common causes of a white tongue are not due to a disease but lifestyle factors. Smoking irritates the lining of the mouth, which can cause it to turn white. This cause of a white coating on the tongue typically goes away once tobacco use is stopped. Not drinking enough water and being dehydrated may also cause a white coating on the tongue. Dehydration due to a temporary illness, such as the stomach flu, may also cause a temporary white film on the tongue.

Bacterial Buildup

Another possible cause of a white coating on the tongue is bacterial buildup. Bacteria in the mouth can form a coating on the tongue, known as a biofilm, that can cause the tongue to be covered in a white coating. Scraping the tongue will remove this coating, and regular brushing of the teeth and using mouthwash will eliminate this cause of a white tongue.