You wake up one morning and your tongue looks black and hairy--don't panic! You've got black tongue, and it's not dangerous.
No one can say for sure exactly what causes black tongue syndrome, but there are generally two main causes: a chemical reaction to bismuth (a main ingredient in Pepto-Bismol) or an overgrowth of bacteria caused by factors such as antibiotics, mouthwashes that contain peroxide or smoking.
Black tongue is usually the result of bacteria buildup that's trapped on your tongue. It gets trapped because the papillae, those bumps on your tongue, get too long and bacteria grows between them. Usually the fiber in your food keeps the papillae short and bacteria-free, but sometimes the papillae grow freely and cause black tongue.
If you have black tongue caused by Pepto-Bismol, don't worry. It should pass quickly. Bismuth is found in several stomach-relief medicines and it sometimes reacts with saliva and turns the tongue black. This is not the same as overgrown bacteria in papillae, but it's just as harmless and it can be treated the same way.
Whatever has caused your black tongue, there are a few things you can do about it. If your mouthwash contains astringents like peroxide, menthol or witch hazel, try switching to a brand without them. Gently brush the surface of your tongue twice a day, or use a tongue scraper. Limit or stop smoking or drinking coffee. These actions should clear up your black tongue.
Make an appointment with your doctor or dentist if you've changed your oral hygiene and your tongue is still black or discolored. If you aren't on antibiotics or taking bismuth medication, you may have a chronic problem that should be looked at. Your doctor or dentist may offer other suggestions and treatment options.