The common causes of morning sickness are oral diseases, liver and gallbladder diseases, digestive diseases, etc. If you have a bitter mouth for a long time, it is recommended that you go to a regular hospital and consult with the relevant professionals if necessary. 1. Oral diseases: such as mouth ulcers, periodontitis, do not pay attention to oral hygiene, etc., bacteria breeding in the mouth, it will lead to bad breath, bitter mouth and other problems. 2. Liver and gallbladder diseases: cholecystitis, gallbladder stones, etc. stimulate the secretion of bile, lying down at night, bile reflux, can also lead to waking up with a bitter feeling in the mouth. 3. Digestive diseases: Gastritis, peptic ulcer and other digestive diseases cause indigestion, which may lead to a bitter mouth. In addition to the above and other reasons, the usual habits and diet are also related, life should pay attention to oral hygiene and cleanliness.