Bad breath, medically known as halitosis, is a common problem. Dietary factors, as well as tobacco and alcohol intake, all can be factors causing bad breath. Poor oral hygiene or mouth infections leads to halitosis. Infections in the lungs, sinuses, or airways can also cause bad breath due to the presence of nasal secretions that may drain into the mouth. Coughing up sputum from lung infections can also lead to bad breath.