Possible causes of indigestion and bad breath include Helicobacter pylori infection, poor dietary habits, and long-term mental and emotional upset. 1. Helicobacter pylori infection: Helicobacter pylori infection often occurs in the stomach and duodenal bulb, can cause gastritis, gastric ulcer, dyspepsia, gastric cancer and other gastrointestinal diseases, but also may lead to halitosis and other symptoms, usually through the carbon 13 or carbon 14 breath test and other methods to confirm the diagnosis. 2. bad dietary habits: often eat cold, spicy, greasy food, can lead to dyspepsia and other digestive diseases, and do not love to brush your teeth, food debris in the teeth fermentation and other bad habits can cause bad breath. 3. long-term mental mood: long-term mental mood will affect the digestive function, leading to the occurrence of indigestion, indigestion is prone to gastroesophageal reflux, resulting in acidic gases from the mouth overflow, the formation of bad breath. There may be other reasons for indigestion and bad breath, so you can go to the hospital for a checkup to make it clear.