Oral thrush — also called oral candidiasis (kan-dih-DIE-uh-sis) — is a condition in which the fungus Candida albicans accumulates on the lining of your mouth. Candida is a normal organism in your mouth, but sometimes it can overgrow and cause symptoms.
Oral thrush causes creamy white lesions, usually on your tongue or inner cheeks. Sometimes oral thrush may spread to the roof of your mouth, your gums or tonsils, or the back of your throat.
Although oral thrush can affect anyone, it's more likely to occur in babies, the elderly, and in people with suppressed immune systems or certain health conditions, or those who take certain medications. Oral thrush is a minor problem if you're healthy, but if you have a weakened immune system, symptoms of oral thrush may be more severe and difficult to control.