Bad breath can be caused by the following:
External factors – foods such as onions and garlic, beverages like coffee and alcohol, and smoking
Poor oral hygiene – where plaque and food debris is left on the teeth
Dentures – plaque and food debris can form on dentures, which need to be cleaned daily
Tonsils – cryptic areas (crevices) in the tonsils can allow food debris to become lodged in the tonsil area
Respiratory tract infections – throat, sinus and lung infections
Dry mouth (Xerostomia) – can be caused by salivary gland problems, medication, mouth breathing, radiation therapy and chemotherapy