First, bad breath is not a disease, but a symptom. When suffering from oral diseases and some systemic diseases, symptoms of bad breath may appear. Etiology: Generally speaking, there are many cases of halitosis caused by oral diseases. For example: dental caries, residual roots, residual crowns, gingivitis (including gingival bleeding), periodontitis (including periodontal abscess), pericoronitis of wisdom teeth, etc. In addition, food impaction caused by misaligned teeth and impacted wisdom teeth can also cause bad breath, and people who smoke and drink will also have the smell of tobacco and alcohol in their mouths. In addition, some systemic diseases can also cause bad breath, and transient oral odor is more common when indigestion occurs. Patients with diabetic ketoacidosis still have rotten apples in their mouths; Uremic patients can smell urine; Patients with liver necrosis have liver odor in their mouths; When organophosphorus poisoning occurs, garlic can be smelled in the mouth. Of course, these are rare in the general population. Treatment: When you feel that you have bad breath or others point out that you have bad breath, you can go to the stomatology department of the hospital or the stomatology department of the physical examination center first to see what causes it, and then further treat the causes of bad breath. For example, filling dental caries, removing residual roots or wisdom teeth, restoring residual crowns, performing periodontal scaling, scaling, anti-inflammatory drugs, orthodontic treatment and so on. Of course, I have to give up smoking and drinking. If it is caused by systemic diseases, please go to the corresponding specialist in the hospital for diagnosis and treatment. Prevention: The most important thing is oral hygiene. After targeted treatment of the above-mentioned causes of halitosis, we should pay attention to keeping the mouth clean and develop a good habit of brushing teeth after meals (pay attention to brushing every face of every tooth exposed in the mouth). If you can't brush your teeth after every meal, you should at least brush your teeth carefully after breakfast and dinner, and rinse your mouth with water when you can't brush your teeth after lunch. In addition, you can also use chewing gum, dental floss, tooth washer, mouthwash, breath freshener and so on. All right, stop talking. I hope you can benefit from the above content, and I wish everyone who reads this article: health, happiness and happiness!