Chlorhexidine is used to treat gingivitis. It helps to reduce the inflammation (redness) and swelling of your gums and to reduce gum bleeding. Gingivitis is caused by the bacteria that grow in the coating (plaque) that forms on your teeth between tooth brushings. Chlorhexidine destroys the bacteria, thereby preventing the gingivitis from occurring. However, chlorhexidine does not prevent plaque and tartar from forming; proper tooth brushing and flossing are still necessary and important.