The tongue is a large muscle with specific functions in the mouth. These functions range from assisting in chewing, swallowing and tasting to helping with speaking, according to Medline Plus. The normal appearance of the tongue is pink with small taste buds over the top surface. Some conditions cause a painless condition called hairy tongue. With hairy tongue, the top of the tongue takes on a rough, black appearance. The black tongue can cause concern for the affected individual but does not pose a health threat.
Papillae
The top of the tongue has papillae, which contain the taste buds. Normally, the papillae shed through normal movement of the tongue while eating and talking. For some individuals the papilla do not shed as usual and continue to grow longer than normal, according to the Mayo Clinic. The longer papillae begin to collect organisms on the tongue and cause a black discoloration on the top of the tongue.
Bacteria and Yeast
Several forms of bacteria and yeast grow inside the mouth all the time. Certain conditions, such as taking antibiotics, may cause and overgrowth of these organisms. The excessive amounts begin to collect on the raised papillae and discolor the tongue. Specific antibiotics can treat the fungal and bacterial infections contributing to the black tongue.
Medication
Medications containing the active ingredient bismuth subsalicylate may cause a black tongue. Bismuth, packaged as a liquid, tablet or pill, helps treat conditions such as an upset stomach, diarrhea and heartburn. Using a toothbrush or a tongue scraper will usually remove the discoloration caused by using products containing bismuth, according to the Merck Manual of Medical Information. Additional medications that may discolor the tongue include some antidepressants and anticolinergic drugs. Anticolinergic medications treat conditions such as asthma, gastritis and Parkinson's disease.
Hygiene
Good and bad oral hygiene may contribute to a black discoloration on the tongue. Not brushing the tongue and teeth properly, dehydration due to a lack of water and breathing through the mouth are all negative factors that may cause a black discoloration on the tongue. The over use of products such as mouthwashes containing oxidizing substances, may contribute to the black appearance of the tongue, according to the Mayo Clinic. These substances include witch hazel, peroxide and menthol.
Smoking and Drinking
Tobacco use from smoking cigarettes and drinking items such as cola, coffee and tea may also cause a darkening of the tongue. Limiting or discontinuing the use of these products helps reduce the tongue symptoms.
