hello thanks for consulting at hcm..Bad breath (halitosis), means that you have an unpleasant smell on your breath that other people notice when you speak or breathe out. causes includes 1) bacteria (germs) or debris that builds up within the mouth,2)associated with a dry mouth is caused by a reduction in the cleansing mechanism of the mouth as a result of reduced flow of saliva, 3)Chemicals in foods can get into the bloodstream, and then be breathed out from the lungs, 4)smoking 5)Crash dieting or fasting-sweet smell on the breath-due to chemicals called ketones being made by the breakdown of fat. 6)Food stuck between teeth. Plaque, calculus and gum disease.Coating on the back of the tongue. treatment includesAim to get into a regular habit of good oral hygiene - in particular, teeth brushing and cleaning between teeth.mouth washes, chewing gums could be used..if it is Halitophobia - fear of bad breath..plz consult a oral periodontist and for halitohobia a psychologist..hope it helps,tc