Images of oral thrush are available at MedicineNet. Oral thrush is caused by a fungal infection that produces white patches and sores in the mouth and throat.
Candida, the fungus that causes thrush, is common in the mouth, digestive tract and skin, but the body's immune system and normal bacteria usually prevent it from causing an infection, according to MedicineNet. These defenses against thrush may be interrupted by a number of different factors, including smoking, dentures, certain medications, pregnancy and illness. Thrush is common in infants and doesn't usually require treatment. Mild cases of thrush in adults are treated with an antifungal mouthwash. Severe cases are only typical in individuals with compromised immune systems and are treated with a systemic medication.