Mouthwash does not have the effect of eradicating bad breath, but it can temporarily mask oral odors due to certain refreshing ingredients contained in the mouthwash. Mouthwash belongs to the oral health care category and is a solution with a variety of added ingredients, such as fluoride and essential oils. Mouthwash is useful for cleaning the mouth, inhibiting plaque and preventing oral diseases. Mouthwash contains certain refreshing ingredients, and its refreshing odor can mask the oral odor of halitosis patients in the short term, but it cannot achieve the purpose of eradicating bad breath. The cause of bad breath is caused by physiological factors, such as do not love brushing teeth, long-term smoking and drinking, love to eat flavorful food, etc., but also may be caused by two major causes of oral disease and digestive system diseases. Oral diseases such as gingivitis, periodontitis, etc., digestive system diseases such as chronic gastritis, Helicobacter pylori infection, gastric ulcers, etc., can lead to bad breath. Therefore, the role of mouthwash is limited, can not be overly relied upon, in the exclusion of physiological causes of bad breath, should be timely consultation and active removal of the cause of the disease, is the key to removing bad breath.