You may find that this condition will respond well to anti fungals like those described on the seb site for use against candida albicans (Thrush). Your therapies have throw the balance of flora in your mouth out of whack. In the normal population this condition can come from a variety of sources, and while it is not pleasant to look at, is not dangerous.

Black hairy tongue (lingua villosa nigra) is the excessive growth of fungi that normally live in the mouth. The exact cause of Black hairy tongue is not known specifically but it is thought that it is a result of an overgrowth of the bacteria normally present in the mouth causing a discoloration of the tongue. This extra tissue can get stained by food or tobacco and become yellowish, brown or black. Bacteria can then accumulate on the finger-like projections from the surface of the tongue (papillae). Some types of bacteria and yeast make red blood cell pigments (porphyrins), which give the tongue a black color. Also, the papillae may sometimes grow liberally, causing the tongue to look as though hair covers it. Some causes of black hairy tongue have been linked to bloom of fungi following antibiotic treatment, ( or for those of us in treatment chemotherapy drugs) which changes the normal bacterial content of the mouth. Poor oral hygiene and the use of medications containing bismuth such as Pepto-Bismol as well as smoking and chewing tobacco can also cause the black discoloration of the tongue. An inappropriate diet, which contains no roughage, especially fruits, vegetables and cereals, can also play a role. ( Not uncommon in those of us that can not eat properly due to our treatments)

The occurrence of hairy tongue varies widely, from 8.3% in children and young adults to 57% in persons who are addicted to drugs and incarcerated. (Not important to you, but an interesting fact). Although hairy tongue is reported more often in males, it is not uncommon in females, especially those who drink coffee or tea and/or those who use tobacco.

People who suffer from black hairy tongue normally spot the condition whilst brushing and mistake it for a potential tumor. In most cases, lesions are noted as part of an intraoral examination performed by a dentist. Hairy tongue clinically appears as an elongation on an area of the tongue. The hairy papillae appear pinkish white, often retain pigments from food, beverages, and candies, resulting in the varying colors associated with the condition (e.g., black, brown, white, green, pink). The tongue has a thick coating in the middle, with a greater inflection toward the back.

You can remove the discoloration by gently brushing your tongue with a toothbrush twice a day. Diluted hydrogen peroxide - one part hydrogen peroxide to five parts water - also may help bleach the color. You can rinse your mouth with it or apply it with a toothbrush. Avoid swallowing the solution. Rinse your mouth with water afterward. [img]http://www.oralcancerfoundation.org/board_images/black_hairy_tongue.tiff[/img]