What the cause of black spot in tongue?

Pigmentation: Normal pigmentation , a condition called geographic tongue or medication your on could cause black spots.

Fungus perhaps: If the black spot is on the tongue it is probably a type of fungus and if there over 10 days see your dentist. If the spot is under the tongue it is probably a varicose vein and nothing to worry about.

Many: Black spots on tongue may be caused by the natural pigmentation of the tongue, but it can also be a warning sign that you are developing a more serious condition such as hairy tongue. I would visit your dentist to have this checked.