Which systemic diseases cause distinct chemical odors in breath?

Some diseases have symptoms related to bad breath. Sinus or lung infections, bronchitis, diabetes, and some liver or kidney diseases may be associated with bad breath.

Bad breath may be the sign of a medical disorder. If your dentist determines that your mouth is healthy, you may be referred to your primary care physician.

Some serious illnesses can cause your breath to have a strange chemical odor. The smell is different from halitosis, or bad breath caused by poor oral hygiene. The breath of someone with uncontrolled diabetes, for example, may have a sweet or fruity odor. It's a sign of a life-threatening condition called ketoacidosis. Liver disease may cause breath with a musty, ammonia-like smell. An intestinal blockage may cause the breath to smell like feces. Breath that has a fishy or urine smell could mean kidney failure. Other possible causes of unusual breath odors include sinusitis, lung abscess, and esophageal cancer.