Bad breath can be caused by improper diet, periodontitis, chronic gastritis, etc. It can be improved by paying attention to oral hygiene and medication. 1. Improper diet: Due to the frequent consumption of some stimulating foods, such as: onion, ginger, garlic, coffee, wine and other foods, the symptoms of bad breath can occur. You should quit smoking and alcohol, and you can use mouthwash after meals to avoid odor. 2. Periodontitis: when the mouth appears periodontitis, the mouth is more likely to breed bacteria, there will be bad breath, you can take cefaclor capsules, azithromycin tablets, cefixime granules under the guidance of the physician to control the infection to relieve the symptoms. 3. Chronic gastritis: when chronic gastritis combined with Helicobacter pylori infection, there will be bad breath, can be under the guidance of the physician omeprazole, amoxicillin, clarithromycin combined with bismuth colloidal, etc. treatment, need to pay attention to part of the population of the penicillin and other drugs allergies, should be under the guidance of the doctor to choose the appropriate antibiotics. After ruling out dietary factors, you should go to the hospital in time to see a doctor to clarify the cause of the disease for further treatment. Avoid self-medication, so as not to cause discomfort, or delay the condition.