The occurrence of bad breath in the morning may be related to factors such as incomplete oral cleaning, periodontal diseases and digestive system diseases. 1. Incomplete oral cleaning: when patients brush their teeth, food residues remain in the gap between the teeth, and the bacteria present in the mouth will ferment the food residues and produce a special odor; in addition, saliva secretion is less in the sleeping state, and the ability of cleaning and transit is weakened, so the symptom of halitosis will be aggravated. 2. Periodontal disease: when the patient suffers from periodontitis, gingival abscess and other periodontal diseases or dental caries, there may be gum pain, oral odor, gingival hyperplasia and other symptoms, the patient’s bad breath in the morning may be caused by periodontal disease. 3. Digestive system diseases: when the patient eats too much food before bedtime causing indigestion, or the patient himself suffers from gastritis, gastric ulcer and other gastrointestinal diseases, may cause bad breath. It is recommended that patients seek medical examination in a timely manner to clarify the cause of the targeted treatment, pay attention to personal hygiene in life, brush your teeth diligently, rinse your mouth in a timely manner after eating, and so on.