If you snore, see an ear, nose and throat specialist. Breathing through the mouth during the night usually results in morning halitosis. There may be an obstruction that can be removed. Long-term smokers may suffer from chronic bronchitis and bronchiectasis. This trouble results in copious amounts of foul-smelling sputum.
Some medical diseases can cause halitosis.
A fishy or mousey odour is present in advanced stages of liver disease. And untreated diabetes produces a sweet, fishy odour. The smell of garlic is usually due to eating it. But the Journal Of The American Medical Association says the too frequent use of selenium can cause bad breath. Selenium sulfide is used to treat dandruff.