What is glossitis and what causes it?

Glossitis is inflammation of the tongue, which may cause the tongue to become sensitive, painful, red and swollen. Possible causes include:
•    A yeast infection (thrush) — usually you would see a white coating on parts of the tongue
•    A virus infection, such as oral herpes
•    Non-infected ulcers called aphthous stomatitis
•    A vitamin or mineral deficiency, especially a B12 or iron deficiency
•    A very dry mouth because of decrease saliva production (from medication or part of Sjögren’s syndrome)