Hello, Thanks for writing to us A tongue with black areas (or black hairy tongue ) on it can be caused by the use of antibiotics, smoking, radiation, frequent use of antacids, use of strong mouthwashes, or use of Pepto Bismol and is usually fungal. It is a harmless condition and can be erradicated by using a toothbrush (good oral hygiene) and the use of a tongue scraper. If you pain associated with it, you Dr might prescribe you something for a secondary infection like the development of yeast. You did not mention any medical problems that you currently have, feel free to respond if needed. I do hope that you have found something helpful and I will be glad to answer any further query.