Parents who discover white patches on their baby’s tongue or cheeks should use a clean washcloth to wipe them away. Parents are urged to bring the baby to a pediatrician if the patches are not easily removed or if they leave raw tissue underneath.

Oral thrush has a distinct appearance. A physician can usually diagnose the condition by looking for the characteristic white lesions on the mouth, cheeks and tongue. When the physician gently brushes away these patches, it will typically reveal tender, reddened areas that may bleed lightly. Physicians unable to visually determine whether thrush is present may perform a KOH prep test (a microscopic examination of scrapings from the mouth) to confirm the diagnosis.

Parents of adolescents and older children with no known risk factors are instructed to seek medical care if their child develops thrush. The physician will compile a thorough medical history and perform a complete physical examination to identify whether the thrush was caused by an underlying condition, such as diabetes. 

Left untreated, thrush can spread into other regions of the body, causing serious complications, such as Candida esophagitis. This condition occurs when thrush extends into the esophagus (which connects the mouth to the stomach). Diagnosis of Candida esophagitis may require additional tests, including:

• Throat culture. The back of the throat is swabbed with sterile cotton and the micro-organisms are studied under a microscope.
  
  
• Endoscopy of the esophagus, stomach and small intestines. A flexible camera captures images of the lining of the esophagus and surrounding areas.
  
  
• X-rays of the esophagus. An image of the esophagus is produced with low doses of radiation.