What Causes Bad Breath
Dental issues. Bad breath can be caused by dental issues such as gum disease or cavities. Crowded teeth or ill-fitting dental appliances can also cause bad breath. See your dentist to rule out any oral care issues as a culprit.
Bacteria. Without proper brushing, flossing, and regular visits to the dentist, bacteria is not being removed from your mouth. The build-up of this sticky bacteria can lead to bad breath. By following the ADA recommendation of brushing twice a day, flossing daily, and routine visits to the dentist, you can keep bacteria in check.
Dry mouth. Lack of saliva creates dry mouth, which may be a side effect of medications, smoking, or mouth breathing or it could be a symptom of an underlying health concern. Talk to your dentist about dry mouth for the best remedies for both dry mouth and resulting bad breath.
Disease. Sinus infections, tonsillitis, respiratory issues and even diabetes can result in bad breath. Your doctor may prescribe medication for these conditions which may make dry mouth, and resulting bad breath worse. Talk to your doctor if your side effects are problematic.
Source: The Perfect Teeth