Chlorhexidine has good substantivity (the ability of a mouthwash to bind to hard and soft tissues in the mouth).  However, chlorhexidine binds to tannins , meaning that prolonged use in persons who consume coffee, tea or red wine is associated with extrinsic staining (. removable staining) of teeth.  Chlorhexidine is rarely associated with other issues like overgrowth of enterobacteria in persons with leukemia , desquamation and irritation of oral mucosa, salivary gland pain and swelling, and hypersensitivity reactions including anaphylaxis. 
Using mouthwash correctly can freshen your breath, help prevent cavities and treat gingivitis. There are two main types of mouthwash that you can choose. Cosmetic mouthwash masks bad breath but does not treat the cause of bad breath. Therapeutic mouthwash, on the other hand, does kill the bacteria that causes bad breath while reducing plaque, gingivitis, and cavities. Once you have chosen your mouthwash, use it once a day before or after brushing, or more often if your dentist instructs you to do so. See Step 1 to learn more about how to use mouthwash for better dental hygiene.