Persistent bad breath doesn’t mean you eat too many onions. Bad breath is a sign of major gum disease. It can also be gasses and odors coming up from gastrointestinal problems. if your halitosis hang on for 24 hrs with out an obvious cause, see your dentist or doctor.
Some diseases that can also cause bad breath include cancer, tuberculosis, syphilis,dehydration, and zinc deficiency. some drugs, including penicillamine and lithium, can cause bad breath too.