Certain medications and smoking can lead to chronic dry mouth, as can problems with the glands that produce saliva.
Certain illnesses, including cancer, can produce consistent bad breath. For example, uncontrolled diabetes can cause a fruity breath odor, while kidney failure results in breath that smells like urine or ammonia, and liver failure causes “fishy” breath. Gastroesophageal reflux disease, or GERD, can also cause bad breath, as can chronic lung infections.
Nose and Throat Issues
Sinus infections often result in bad breath because of sinus drainage down the throat, which results in a bad mouth odor. Respiratory infections such as bronchitis can also produce sputum with a bad odor. A child with otherwise normal breath may develop bad breath when a foreign object like a small bean is stuck in the nose.
Some activities such as smoking or using other tobacco products can lead to periodontal disease and dry mouth, which can cause bad breath. Severe dieting or fasting can also cause unpleasant, fruity-smelling breath from a breakdown of chemicals in the body. And taking vitamin supplements, especially in large doses, can also lead to bad breath.
If you have bad breath, using a mint or chewing gum can temporarily mask the problem, but it won’t cure the underlying cause. If bad breath persists and there is no obvious cause, such as smoking or eating certain foods, or if you have signs of a respiratory infection, be sure to talk to your doctor. And remember to mention if people around you have commented on a particular odor.