Children’s bad breath and unpleasant odor may be related to poor oral hygiene, oral diseases, digestive system diseases and other reasons. 1. Poor oral hygiene: If children do not pay attention to oral hygiene, such as long-term not brushing their teeth, etc., can lead to a large accumulation of food residues in the oral cavity under the action of bacteria fermentation, can produce an unpleasant odor. 2. Oral diseases: such as dental caries, if a child has dental caries, it can lead to the accumulation of food in the cavity, which is not easy to clean up, and the phenomenon of bad breath can occur. 3. Digestive system diseases: such as chronic gastritis, food emptying time in the stomach is delayed, under the action of bacterial fermentation, there may be out of breath odor phenomenon. If the child has other uncomfortable symptoms, parents are advised to take the child to the hospital in time to clarify the cause and standardize the treatment under the guidance of the doctor.