(Hairy tongue; Lingua nigra; Hyperkeratosis linguae)
This is a rare, benign condition of the dorsal surface of the tongue. It is usually situated in front of the circumvallate papillae but may be found on other parts. The condition may be in the form of a black discoloration; a few instances of brown, yellow and blue coloration have been reported. However, it is more common to find thin, filiform, dark-colored projections on the pigmented surface. These have been likened to hairs, seaweed, tendrils and lashes. Usually subjective sensations are absent except a peculiar but not very offensive taste in some well developed cases. This malady is found both in children and adults.
Etiology, Prognosis and Treatment. While the causes are unknown, irritating mouth-washes, excessive smoking and stomatitis resulting from mercury might bear a causal relation. Black tongue does not call for treatment for, although it is variable in its duration and behaviour, it usually disappears spontaneously sooner or later.