The most common cause of malodour Oral is the accumulation of scraps and plaque bacteria on the teeth and tongue caused by oral hygiene is poor and the gums (gingivitis) and periodontal disease (gingivitis / periodontitis). Although most types of inflammation of gingivitis and periodontitis can cause acute necrotising gingivitis malodour swelling. (Trench mouth disease Vincent's) most prominent cause bad breath.