Bad breath can be caused by indigestion, oral diseases, and endocrine disorders. There are different treatments for different symptoms. 1. Indigestion: As food is not fully digested and absorbed, it stays in the stomach for too long, and the fermentation of the food will form an odor, which leads to the phenomenon of bad breath. It is recommended that patients eat a light diet and avoid spicy and stimulating foods, such as onions, garlic, leeks and so on. 2. Oral disease: decay in the teeth, periodontal disease will make the gums in an inflammatory state, the mouth will produce a rotten foul odor. It can be treated by filling treatment or periodontal treatment or the use of anti-inflammatory drugs under the guidance of the doctor to assist in the treatment, such as roxithromycin, amoxicillin, metronidazole and so on. 3. Endocrine disorders: caused by too much or too little hormone production. Pay attention to oral hygiene, ensure regular work and rest, pay attention to dietary health, eat more fiber-rich foods, such as brown rice, green vegetables, lettuce and so on. Usually must diligently brush your teeth, use mouthwash, maintain oral hygiene, eat a light diet, do not heavy taste, the situation is serious should immediately go to the hospital for treatment, the drug needs to be used under the guidance of a doctor, not to take on their own.