<s>[INST] Hello gd morning my wife she had black spot on the surface layer of tongue for almost 8 - 9 months treatment done but no cure. when she eat food it pain and that black portion has become little thin as compare to other part of tongue. Size of black spot is 1 cm round. please suggest me what to do? [/INST] Hello, Thanks for consulting Chat Doctor, Read your query, as your wife had tender black spot on tongue this can be due to poor oral hygiene there is deposition of food, Chat Doctor.  I will suggest you to consult oral surgeon and go for proper examination of oral cavity and tongue and rule out the cause of discoloration of tongue, if needed go for investigation Cytology of blackish portion of tongue. In meantime maintain proper oral hygiene, use tongue scraper to clean your tongue, use mouthwash regularly. Hope this will help nourishing you good health.   </s>