Bitter mouth and dry mouth back pain may be reflux esophagitis, dry syndrome and other diseases. 1. Reflux esophagitis: This symptom occurs when gastric acid refluxes into the esophagus, pharynx and even the oral cavity due to the dysfunction of the lower esophageal sphincter and the decrease in the barrier ability of the esophageal mucosa, stimulating the local mucosa. 2. Dry syndrome: autoimmune system dysfunction, produce antibodies against their own salivary glands, lacrimal glands and other tissues, resulting in reduced secretion of salivary synthesis, dry mouth and bitter mouth due to lack of water in the oral cavity; skin rashes, muscle pain and other symptoms occur after involving the skin and muscles of the back. Bitter mouth, dry mouth, back pain may be related to a variety of factors, it is recommended to consult a doctor to clarify the diagnosis.