Bad breath after staying up all night may be related to body fire and dietary factors. 1. Physical fire: If you often stay up late, irregular work and rest time, due to mental stress, and physical rest is not good, it is easy to cause physical fire, stomach fire, the typical symptoms of bad breath, nausea, stomach burning pain, so the phenomenon of halitosis occurs late at night. 2. Dietary factors: usually stay up late will intake of refreshing drinks and food or smoking, because smoking itself will cause bad breath, in addition to stay up late during the intake of food is easy to remain in the teeth, because there is no timely cleaning, resulting in bacterial growth, putrefaction of food residues, bad breath can occur. Halitosis should first maintain oral hygiene and cleanliness, develop the habit of brushing teeth in the morning and evening and rinsing mouth after meals, and if it persists for a long time, it is recommended to consult a doctor in time to do a detailed examination to clarify whether there are disease factors.