Black hairy tongue is a temporary, harmless oral condition that gives the tongue a dark, fury appearance. It is mainly caused by bacteria or fungi in the mouth, which makes the tongue black and hairy.
Symptoms: Due to growth of fungi it causes burning sensation called glossopyrosis. Some even feel tickling on the roof, nausea, metallic taste and even bad breath.
Treatment: Maintenance of proper oral hygiene by brushing twice a day. Drinking plenty of water and taking roughage food.
There are many people suffering due to this, but relevant statistics have not been found till date.