bad breath can be caused by the following: Poor dental hygiene — Infrequent or improper brushing and flossing can leave food particles to decay inside the mouth. Infections in the mouth — Periodontal (gum) disease. Respiratory tract infections — Throat infections, sinus infections, lung infections, smoking drinking,, chewing tobacco products etc. Avoid all the habits which cause bad breath, use medicated mouth wash (chorhexidine mouth wash), brushing in the night before bed it good. Elaichi or clover leaf chewing once a day will helps to reduce bad smell.