①80% to 90% of bad breath is caused by oral problems, and the rest are mostly related to the nasal cavity and tonsils. Helicobacter pylori has not been determined to cause bad breath. ②The main odor in the oral cavity comes from the decomposition products of bacteria. Bacteria in the oral cavity can release foul-smelling “volatile sulfides”, including hydrogen sulfide, methyl mercaptan, indole, etc., by breaking down food residues and epithelial cells shedding from the oral cavity. It emits a bad smell. Therefore, the accumulation of bacteria is the key to bad breath. Insufficient brushing time (less than 2 minutes), not using dental floss to clean between teeth, etc., can easily lead to inadequate cleaning and allow bacteria to accumulate. Dental calculus, cavities of tooth decay, missing teeth, bad dentures and other places are prone to accumulate large amounts of bacteria and cause bad breath. In addition, habits such as smoking, long-term use of antibacterial mouthwashes, drinking and coffee may also cause bad breath. As for Helicobacter pylori, more evidence currently shows that the concentration of volatile sulfide produced by the decomposition of Helicobacter pylori in the gastrointestinal tract is very low, and it is unlikely to produce bad breath. In addition, most Helicobacter pylori infections have no obvious symptoms, leading to food retention and increasing gastroesophageal reflux in a very small proportion. Usually, bad breath occurs only after hiccups and pantothenic acid, and gastrointestinal problems need to be suspected. ③So if you want to effectively prevent bad breath, you must first check with a doctor. If you have tooth decay, you can treat it, and if the tooth is missing, you should also strengthen your cleaning. For example, brush your teeth in the morning and evening, rinse your mouth after meals, Fluoride toothpaste, and don’t forget to floss between your teeth and wash your teeth regularly.