Why does a 9-month-old baby have bad breath?

The main causes of bad breath in a 9-month-old infant include poor food absorption and oral diseases. Infants have immature gastrointestinal functions, and when food is not fully digested and absorbed, it can lead to foul odors, along with symptoms such as bloating, nausea, vomiting, and abnormal bowel movements. Oral odor is primarily caused by conditions such as oral ulcers, oral herpes, or abnormal oral development. Parents are advised to take their baby to the hospital promptly for a physical examination by a pediatrician or dentist, who can provide targeted treatment.