The causes of halitosis can be divided into two.

Systemic causes: when there is a major disease that affects our economy corporal.
Local causes: the most frequent and are due to diseases of the digestive tract and in the head and neck as diseases of the mouth, teeth, gums, nose or throat. The expert noted that people with a systemic problem (generalized) in many cases do not realize their halitosis, for example, people with diabetes may have an odor of acetone, patients with liver disease can have a breath smell of ammonia. Tonsillitis, bacterial plaque, respiratory infection, sinusitis, rhinitis are just some of the conditions to try to combat this problem. Deschamps explains that "the only symptom so far this condition is bad breath" and depending on the disease that fueled the basis of halitosis there may be a treatment. Approximately 20 percent of patients will be consulted by halitosis. Most of the causes of halitosis are due to diseases of the gums and teeth followed by upper respiratory infections. The decrease in the flow of saliva in the mouth has been identified as a cause of "bad breath in the morning." The morning halitosis occurs because, during sleep, you stop producing saliva and the temperature of the mouth is more stable to keep it closed. This keeps your mouth clean of waste. Without saliva, the mouth is dry and dead cells and bacteria adhering to the tongue and inside the cheeks. This will produce odors.