Infants with bad breath may be caused by oral hygiene problems, systemic diseases and other reasons. 1. Oral hygiene problems: usually some parents have little awareness of oral health care for infants, and even think that infants do not need oral hygiene cleaning, resulting in poor oral health of infants, the fermentation of food residues to produce a bad smell, or even oral ulcers and so on, leading to infants with bad breath. 2. Systemic diseases: the general baby’s body resistance is poor, the gastrointestinal system is weak, easy due to improper diet, body cold, abuse of antibiotics respiratory inflammation, children’s nasal foreign body and other respiratory diseases, resulting in food stagnation, indigestion, intestinal flora imbalance, resulting in the formation of ulcers and pus, leading to bad breath in infants. There are many other reasons why infants have bad breath, and it is recommended that patients seek timely medical treatment to standardize treatment after clarifying the cause of the disease.