The Centre for Digestive Diseases investigates causes of bad breath (Halitosis). The causes include bacterial overgrowth on the back of the tongue but more commonly bacterial overgrowth of the bowel flora. The Halimeter test can detect several volatile gases which are created by bacteria mainly in the colon. After measuring the level of these gases the patients can then be treated to reduce gas production either in the bowel or on back of the tongue or treating both sites to reverse chronic bad breath.