Baby’s bad breath may be caused by not doing a good job of oral hygiene, thrush and indigestion. 1. Failure to do oral hygiene: If parents do not clean the baby’s mouth, resulting in food corruption emitting a foul odor, it will cause the baby’s mouth with bad breath phenomenon. 2. Thrush: caused by Candida albicans infection, which can lead to damage to the baby’s oral mucosa, accompanied by the phenomenon of pain, but also cause the baby to have bad breath. 3. Indigestion: Due to weak gastrointestinal development and poor digestion, eating too much may cause food to stagnate in the gastrointestinal tract and cannot be discharged, and when the food breaks down, it will cause gas to move upward and cause bad breath. When the baby has breath for a long time, it is recommended to go to the hospital in time to find out the cause of the disease, and according to the cause of the standardized treatment.