Hairy tongue, medically known as lingua villosa, is generally a harmless condition that alters the appearance of the tongue, making it appear discolored and furry. Hairy tongue is also commonly referred to as black hairy tongue (lingua villosa nigra), but the tongue discoloration may appear white, brown, pink, or green. The color of the tongue depends both on the underlying condition plus the presence of any additional factors, such as the type of food consumed. Hairy tongue is caused by irritation of the surface of the tongue, leading to the elongation of the papillae that are normally present on the surface of the tongue along with an absence of shedding of superficial cells that is typically facilitated by toothbrushing or dietary factors. A number of different conditions can cause the development of hairy tongue.