Infants with thrush often experience symptoms such as white patches on the tongue and the inside of the mouth that appear to look like cottage cheese, explains WebMD. The white patches cannot be wiped away and may bleed when rubbed. Infants may also have difficulty swallowing and a sore mouth and tongue when suffering from thrush.
Thrush may also contribute to a poor appetite in infants and an increase in fussy behavior, according to WebMD. Some patients may also develop diaper rash when yeast that causes thrush is expelled in the baby's stool. Babies who develop an infection that spreads beyond the esophagus from thrush sometimes develop a fever.
Thrush can affect older adults and people with weak immune systems, but it is most common in toddlers and babies, according to WebMD. Thrush is an infection that affects the mouth when yeast or candida fungus is present. Candida fungus is present in the skin, mouth and digestive tract within most healthy people, but an infection occurs when the fungus grows out of control. The balance of fungus growth is impacted by certain illnesses, medications and stress, causing thrush to develop in infants and adults. The infection can travel to other parts of the body.