If normal healthy people do not brush their teeth in time before going to bed, saliva secretion will be reduced at night and oral bacteria will multiply, which will lead to bad breath and bitterness in the morning, and the symptoms can be improved by timely brushing. If you have gingivitis, periodontitis, dental caries, dental calculus and other oral diseases, it will lead to a large number of bacteria reproduction in the mouth, secretion of foul-smelling substances, bitterness and bad breath is particularly obvious, you need to actively treat oral diseases. Improper diet and constipation can also lead to bitterness and bad breath. Long-term symptoms of bad breath may also be caused by organic diseases such as liver and gallbladder disease, diabetes, cancer, etc. It is necessary to go to the hospital to clarify the cause of the disease through relevant examinations and to treat the cause.