17 different types of bad breath and what causes them

Bad breath can sometimes be a red flag for a range of conditions from diabetes to syphilis that has nothing to do with the mouth. Fetid, stinky breath: Syphilis — a sexually transmitted infection caused by Treponema pallidum bacteria — can make a patient’s breath smell really bad. Sweet and musty: Homocystinuria, a genetic disease in which the body can’t process the amino acid methionine, can make the breath smell sweet and musty. And it can also make the patient’s breath smell like sweaty feet. Smells like old blood: Any disease or disorder related to the blood — example, bleeding disorders, coagulation disorders, and red blood cells disorder — can make a patient’s breath smell like blood or like a surgical wound that has just started healing.