Hi.. Thanks for the query.. Black spots on tongue can be due to a number of causes, one is excessive accumulation of melanin pigments that are normally present and can be accumulated more in certain areas of body.. Other is poor maintenance of oral hygiene that can cause black hairy tongue due to accumulation of bacteria and fungal overgrowth over the tongue leading to dark spots.. Another cause can be intake of metallic compounds containing Bismuth. Allergies can also cause staining of tongue.. So it is not necessarily any serious problem.. But I would still suggest you to consult an Oral Surgeon and get evaluated and a thorough clinical evaluation should be done.. As of now you can start cleaning the tongue with a tongue scraper and gargle with 1:1 solution of hydrogen peroxide and water.. You can also gently clean your tongue with a soft toothbrush by dipping in the hydrogen peroxide solution.. Eat hard foods as they clean the tongue with the rubbing action.. Hope this information helps.. Regards.