Bad breath can be caused by a bad stomach or a bad liver. Helicobacter pylori infects the organism and causes gastrointestinal diseases, chronic gastritis, peptic ulcer and other diseases that cause sour odor in the mouth, and pyloric obstruction, advanced gastric cancer can also have symptoms of bad breath. Liver function is seriously damaged, methionine after digestion and bacterial action will release methyl mercaptan, dimethyl sulfide resulting in hepatic odor, hepatic odor can be excreted through respiration or urine, which can cause similar bad breath; and, patients with cirrhosis are also prone to oral infections, and oral infections can also cause halitosis. Therefore, halitosis may be caused by bad stomach or bad liver. In addition, bad breath can also be caused by not paying attention to oral cleaning in daily life, eating garlic and other foods. If you have bad breath that is not relieved by oral cleansing, you can go to the hospital and ask your doctor to determine the cause of your bad breath.