<s>[INST] Hello Dr, my baby is 4 months old and the back region of her tongue turned blackish blue. I took her to the Dr but was told that she might have bit her tongue. But it is in the back region of the tongue and she is not toothing yet. is there some problem? [/INST] Hi. Thanks for writing on Chat Doctor. Blackish blue discoloration of tongue can be due to a condition known as Black Hairy Tongue, and it can occur due to a number of conditions like overgrowth of bacteria and fungus over the tongue, entrapment of dead cells over the tongue papillae and when the Papillae do not shed as per its normal cycle and there is elongation of the papillae and more of debris and dead cell entrapment as well as more growth of bacteria and fungus. You should consult an Oral Physician or Periodontist and get evaluated and in case of fungal infection along with maintaining good Oral hygiene you will have to take antifungal medication like Candid mouth paint. Clean the tongue gently using an ultras oft toothbrush. Hope this information helps. </s>