Dry and smelly mouth may be due to gastrointestinal dysfunction, gingivitis or periodontitis, reflux esophagitis, dry syndrome and other reasons. 1. Gastrointestinal dysfunction: excessive psychological stress, lack of rest, unhealthy diet, cold abdomen and other factors lead to gastrointestinal peristalsis, indigestion, so the mouth will be dry and smelly. 2. Gingivitis or periodontitis: long-term non-brushing of teeth leads to the surface of the teeth food residues, bacterial adherence, the formation of calcified stones leading to periodontal disease, so the mouth is dry and smelly. 3. Reflux esophagitis: stomach acid and other stomach contents through the esophagus reflux into the throat, mouth and other parts of the mouth and lead to dry and bitter. 4. Dry syndrome: an autoimmune disease that leads to abnormal secretion of the salivary glands, which reduces the production of saliva and makes the mouth dry and smelly. Dry and smelly mouth may be related to a variety of factors, it is recommended to consult a doctor for a clear diagnosis.