Bitter breath and bad breath in the morning may be caused by bile reflux, indigestion, self-factors, poor oral hygiene and other reasons. 1. Bile reflux: relaxation of the lower esophageal sphincter can cause the stomach odor, contents, gastric acid, pepsin, and bile reflux to flow back into the mouth. This is especially noticeable at night. The lack of gravity at night to counteract reflux can lead to bitter, bad breath when you get up in the morning. 2. Indigestion: poor function of the gastrointestinal tract can cause indigestion, intestinal flora disorders, constipation, which can also cause the symptoms of bitter breath and bad breath in the morning. 3. own factors: if the patient usually do not pay attention to oral hygiene, such as not brushing teeth before going to bed at night, the oral bacteria breeding, decomposition of food residues will produce a special odor, resulting in patients with bitter halitosis in the morning. 4. Poor oral hygiene: there is a large amount of dental calculus and plaque in the mouth, long-term bleeding from brushing, and occasional pus overflow from the gums, which will lead to symptoms such as bitter mouth and bad breath in the morning. If the situation of bitter mouth and bad breath in the morning occurs, it is recommended that parents should bring their babies to the doctor in time, ask the doctor to clarify the cause of the disease, and if necessary, carry out the corresponding examination.