Black tongue is a condition in which the surface of the tongue turns dark or black. The tongue may also become rough, and develop a hairy appearance, in which case the condition may be known as black hairy tongue. Although black tongue looks unsightly, it is not usually harmful, and it can be resolved with care at home in most cases, although in some instances it may be necessary to see a doctor for a prescription.

There are a number of causes for black tongue. It can be caused by an overgrowth of fungi or bacteria in the mouth, in which case drugs may be needed to limit the growth, and it has been linked with a number of medications including antibiotics and drugs which contain bismuth, which may cause black tongue as a side effect. Smokers, the elderly, people with poor oral hygiene, and people undergoing radiation treatments are all at risk for developing black tongue.

The treatment for black tongue usually involves scraping the tongue with a tongue scraper, or brushing it with a toothbrush, in addition to observing better oral hygiene, with regular tooth brushing, flossing, and use of mouthwash. If the black tongue is persistent, a doctor may take a culture of the black growth on the tongue to find out what it is, and recommend a medication to manage it.

Also known as melanoglossia, this condition usually starts out as a series of dark spots on the tongue, which gradually merge to form a large dark patch. The tongue may feel heavy or rough in the mouth, and the sense of taste can be disrupted. In some cases, the papillae, also known as the tastebuds, can become swollen and elongated, contributing to the rough appearance of the tongue. People sometimes develop black tongue overnight, often after taking a medication and not brushing their teeth, and it can be startling to wake up to.

When black tongue develops, patients may opt to try self care at home to manage the problem. If a patient is on medication, it's a good idea to report the black tongue to the doctor, just in case it's an unexpected side effect. Likewise, patients with compromised immune systems should call their doctors about any unusual medical symptoms or conditions which emerge, so that the doctor can decide whether or not the patient needs to come in for treatment. As with all conditions which can be managed at home, if the issue does not resolve after several days to a week of treatment, a doctor should be consulted.