Thrush usually develops suddenly, but it may become chronic, persisting over a long period of time. A common sign of thrush is the presence of creamy white, slightly raised lesions in your mouth - usually on your tongue or inner cheeks but also sometimes on the roof of your mouth, gums, tonsils, or back of your throat. The lesions, which may have a "cottage cheese" appearance, can be painful and may bleed slightly when you scrape them or brush your teeth. In severe cases, the lesions may spread into your esophagus, or swallowing tube, causing: