Actually talking each humanbeings are badbreathres. Oral cavity contains millions of anaerobic bacteria like fusobacterium as well as actinomyces which functions on the protein of food supplies and putrifies them. This procedure results in the development of offenssive gases like hydrogen sulphide,methyl mescaptan,cadaverin,skatol,putrescine etc producing bad smell. If oral hygiene isn't maintained properly all will suffer from bad breath. A lot of us control this by regular brushing,tongue cleaning and gargling.