One-and-a-half year old babies with bad breath may be caused by indigestion, oral diseases, physiological factors and other factors. 1. Indigestion: If you don’t pay attention to your daily diet, you may suffer from food retention and indigestion, which will increase the burden of gastrointestinal function and cause bad breath. 2. Oral disease: parents do not develop good hygiene habits, do not help babies brush their teeth after meals, due to food residues lead to periodontitis, gingivitis, dental caries, etc., resulting in bad breath in infants. 3. Physiological factors: daily drinking less water, salivary flow rate decreases, can also lead to dry oral mucosa, if not timely replenishment of water, bacteria are prone to reproduce, resulting in bad breath. One and a half year old infants with bad breath, there may be other reasons, it is recommended to go to the hospital in a timely manner, improve the examination to clarify the cause of the disease, to give targeted treatment or treatment.