Heavy mouth odor and bad breath may be caused by poor oral hygiene, oral diseases, digestive system diseases, etc. 1. Bad oral hygiene: If the oral cavity is not cleaned properly, it will cause bad breath, so that a large number of bacteria grow in the oral cavity, bacteria will continue to ferment and reproduce, which will lead to heavier breath in the mouth. 2. Oral disease: oral disease is an important factor in causing heavy breath, such as dental calculus, periodontitis, periodontal abscess, etc. will lead to the continuous growth of harmful bacteria in the mouth, the balance of the oral flora is damaged, which will have the release of odor. 3. Digestive system diseases: gastroesophageal reflux, dyspepsia, gastritis, Helicobacter pylori infection and other diseases can cause bad breath problems. It is recommended that patients go to the hospital in time for examination and receive relevant treatment according to the cause of the disease to avoid aggravation of the condition.