My mom has had a bitter, sour, metallic taste in her mouth for years. it is now also dry. she's been to many dentists and mds. no answers?

Abnormal mouth taste: American medical or dental textbooks, several asian medical texts made reference to sour, bitter, and metallic tastes associated with the rear of the tongue. This is very logical because the bacteria that produce the sulfur compounds breed on the back of the tongue, which is the area that is susceptible to sour, bitter, and metallic tastes.

Autoimmune Disorder?: Your mom may be suffering from sjogren's syndrome. I have had several patients with similar symptoms and a correct diagnosis and by a physician proper medications have helped tremendously.

Oral medicine: She should see an oral medicine specialist. They are trained to help patients just like your mom. They are dentists who have gone back to school and specialized in oral medicine. Good luck.