Hairy Tongue is a medical
disorder where the
tongue turns discolored and the
filiform papillae (the bumps on your
tongue) excessively grow. It's also known as "Black Hairy Tongue" or "Lingua Nigra" (Black Tongue?) in some medical texts.
A Hairy Tongue appears yellow, brown, black, or blue. It looks hairy or speckled. The papillae (bumps) also form a V shape at the back. Both of these signs may spontaneously disappear, and in some cases, recur. Often, patients complain of a bad taste in their mouth.
What causes it? It can result from changes in the oral flora (the germ environment in your mouth) caused by antibiotics. Or the patient could just have poor hygiene, and the filiform papillae (the tongue bumps) become longer. Some cases can result from reduced saliva or from fever. Tobacco can also stain the tongue.
Its epidemiology is nothing special, it can affect men or women, kids or adults. It is, however, sorta rare. Standard treatment includes avoiding irritants and substances that can sensitize the tongue. You desquamate (peel) the outer layer of the tongue by brushing your tongue with a soft-bristle brush. The symptoms usually disappear once the person stops taking the antibiotics or mouthwash and the regular flora grows back. In some cases, it goes away spontaneously.
For more information, consult a doctor or Ear-Nose-Throat specialist.
Source:
Physicians' Guide to Rare Diseases
The National Organization for Rare Disorders - rarediseases.org