Children with bad taste in the mouth may be caused by oral diseases, digestive system diseases, excessive consumption of protein and sugary foods. 1. Oral disease: children with a bad taste in the mouth, need to pay attention to exclude whether the child has oral diseases, such as dental caries, local mucosal ulcers, gingivitis, etc. And parents should pay attention to the child’s oral hygiene. And parents should pay attention to children’s oral hygiene. 2. Digestive system diseases: when the child suffers from digestive system diseases, such as chronic dyspepsia, chronic gastritis, gastroesophageal reflux, intestinal obstruction and other diseases, it is also easy to cause an abnormal taste in the mouth. 3. Overeating protein and sugary foods: If a child eats too much protein or sugary food at one time, which exceeds the baby’s digestive function, it is easy to cause the food to stay in the gastrointestinal tract for a long time and fermentation to cause a bad taste in the mouth. If a child regularly develops a bad taste in the mouth, parents are advised to take the child to the hospital as soon as possible to find out the cause. Some special diseases can also cause special odor, parents need to pay attention to, timely medical treatment, such as ketoacidosis will have rotten apple flavor.