The causes of bad breath after waking up in the morning are oral local factors, digestive system infections, and inflammation in other parts of the body. 1. Oral local factors: such as oral infections, gingivitis, etc., mostly due to anaerobic infections, anaerobic bacteria metabolism produces ammonia resulting in bad breath. 2. Digestive system infections: such as Helicobacter pylori infection, which is an anaerobic infection, anaerobic bacteria in the digestive system reproduction, metabolism and ammonia, and then discharged from the oral cavity, so the symptoms of bad breath. 3. other parts of the inflammation: such as nasal or throat anaerobic infection, anaerobic bacteria metabolism of ammonia can be discharged from the oral cavity, thus producing bad breath. People with bad breath should consult a doctor in time to find the primary disease and actively treat it.