If you have black hairy tongue, it looks like your tongue is stained. Actually, "black hairy tongue" is somewhat of a misnomer; the condition can cause a variety of colors including white, yellow, pink, green, brown and black depending on what is contributing to the problem. It is harmless, but looks quite alarming. The tongue can also discolor due to eating certain foods (like beetroot, foods with artificial colors, or vegetable dyes). However, while discoloration caused by food can be brushed off with a toothbrush, the discoloration due to hairy tongue cannot be brushed off. If you have a black hairy tongue, it's caused by one of two things: either a bacteria overgrowth or yeast overgrowth. Overgrowth of bacterial or fungal organisms for any reason can cause black hairy tongue; sometimes, those reasons can be elusive and it can be a detective hunt to figure out what may be causing it. This informative book contains the causes of black hairy tongue and treatment options to eliminate it in simple steps.