<s>[INST] Hi, my 30 months old daughter is sick for 3 weeks (flu, caughing). As per doctor s advise, for 7 days she got antibiotics, 2 times a day. Three days ago, her tongue start turning black. Could you please tell me what is the cause and what can I do about it. Thanks. [/INST] Hi, Tongue turning black could be side-effect of linezolid antibiotic if it has been used. Otherwise, no specific reason can be attributed and keep her well hydrated and it will go off in 4 to 6 weeks. Hope I have answered your query. Let me know if I can assist you further. Take care Regards, Dr Sumanth Amperayani, Pediatrician, Pulmonology </s>