Black tongue is a condition that is not common in healthy people, but is not cancerous and is easily treated by regularly cleaning and/or scraping the tongue when you brush your teeth.
The tongue is a muscle that has hundreds of tiny bumps on it called papillae. This is where your taste buds are. The papillae constantly grow and shed the older cells as they do.
Sometimes your papillae don't shed the old cells and it causes them to grow long and give off a hairy appearance. If this happens, debris and bacteria get trapped on your tongue and the bacteria grows, giving your tongue the appearance of being black.
There are certain risk factors that could increase your chance of getting black tongue though they are not specific causes of the condition. The risk factors include smoking, taking antibiotics, some of which upset the bacteria balance in your mouth, chemotherapy and/or radiation therapy of the head or neck, uncontrolled diabetes or other systemic diseases.
If you don't take good care of your teeth and gums, you are at a higher risk of developing this condition, particularly if any of the other risk factors pertain to you.
Black Tongue is easily treatable by using a toothbrush that has a tongue cleaner on it. In severe cases you may need a tongue scraper. The condition usually disappears within a couple of weeks as does the bad breath that accompanies it.