Black Tongue As A Medical Condition
The discoloration may start near the tip of the tongue in some cases but generally, it spreads at the base of the tongue in the region of the taste buds. The condition may remain confined to one part or involve the whole of the tongue. Although it causes intense worry to the person having it, black tongue is generally a harmless condition which does not last long. 
Finger-like projections called ‘filiform papillae’ are located around the taste buds. With normal daily wear and tear, these papillae are shed off. But sometimes, due to certain conditions, this normal process of shedding of papillae is altered. The papillae then keep growing in size. Food particles get stuck in these outgrowths. The food debris becomes a breeding ground for many bacteria and fungi, giving rise to a dark, fuzzy look called as the black tongue. The term black tongue is a misnomer, as the bacterial action may give rise to various shades of yellow, white, brown or even green. 
Causes Of Black Tongue
A black tongue can be the result of many factors, the most common of which is poor oral and dental hygiene. Having one too many cups of tea or coffee can also stain the teeth and tongue black. When a person eats a diet which has an adequate amount of roughage, like fruits and green vegetables, the long papillae are scraped off. However, if the diet lacks this vital component and is based on soft food, either because of personal choice or in case of loose or missing teeth as in the elderly, there is a higher likelihood of developing a black tongue. Not drinking an adequate amount of water may also lead to this condition. 
Nicotine present in tobacco and cigarettes is known to discolor the teeth and tongue. The bacteria normally found in the mouth start increasing rapidly as the smoke of cigarette changes the natural oral conditions. This unchecked bacterial growth results in black tongue.[1,2]
Certain medications containing Bismuth salicylate which aid digestion, and some mouthwashes which contain menthol or peroxide also stain the tongue black. In some cases, the presence of black tongue can be attributed to asthma inhalers. Rarely, the condition can develop in people who are depressed, under nervous tension, or have systemic diseases like diabetes. 
Bacterial or fungal infections of the mouth can also result in black tongue. If all the above-mentioned conditions are ruled out, then the doctor may like to examine the patient for Sjogren’s syndrome, a very rare but grave illness.  A black tongue may also be associated with a compromised immune system and can be seen in patients receiving radiotherapy to head and neck regions. 
Patients with oncological disorders, smokers, black tea drinkers, and those with poor oral hygiene are more likely to develop black hairy tongue . This condition also correlates with gender and age predilection:
- Men are about three times more commonly affected than women
- Studies show a prevalence of nearly 40% in patients over the age of 60 
Symptoms And Diagnosis Of Black Tongue
The main black tongue symptoms, apart from discoloration, include a change in the feel of tongue’s surface, bad oral odor, and loss of taste. Staining is the single most important black tongue symptom. This discoloration starts as small spots and may spread to cover large areas on the dorsum of the tongue. It may be black, brown, green or white in color. The bacterial and fungal growth may result in a fuzzy or hairy texture of tongue, another black tongue symptom. 
One more symptom is the loss of taste as the disease primarily involves the papillae around taste buds. It becomes hard to differentiate between the taste of different things and the patient may even complain of metallic taste in the mouth. 
A foul smell emanating from the mouth, also known as halitosis, may again be a black tongue symptom. This bad smell does not subside easily even when using mouth fresheners, as it is caused by an underlying infection in the mouth. In some patients, gagging may be seen.
Discoloration associated with halitosis is a sure giveaway to establish the diagnosis of black tongue although sometimes an examination of a scraping from the tongue may be necessary to identify the underlying bacterial or fungal infection.
Treatment Of Black Tongue
Black tongue is a temporary condition which resolves on its own once the incriminating factor is removed.
Maintaining oral hygiene is the single most important step in black tongue treatment. It is essential to brush your teeth twice daily, to floss them and to clean the tongue with a tongue scraper. Eating an adequate diet with a sufficient quantity of roughage is imperative. It is essential to drink at least two liters of water every day to maintain proper hydration.
If the condition is due to Bismuth present in various digestive aids, then it improves within three days of stopping the medication. If mouthwash is found to be the incriminating cause, it is better to change it to a non-menthol or non-peroxide one. It is never too late to give up on nicotine.
If the black tongue is because of some antibiotic medication, it is better to seek advice from your physician instead of discontinuing it voluntarily.
A black tongue due to the use of an asthma inhaler can be remedied by switching to a different inhaler in consultation with the doctor. Antibiotics or antifungal medicines advised by the doctor for black tongue treatment provide relief in cases where a bacterial or fungal infection is the cause behind the condition.
Patients suffering from systemic illnesses like diabetes, cancer or immune-deficiency syndromes should visit the dentist regularly for proper oral check-ups.
Some people "prescribe" pineapple as a black tongue treatment. In this treatment, small pieces of pineapple are to be sucked for about forty seconds keeping them near the base of the tongue. They are then slowly chewed over a period of eight minutes. This process is to be repeated two times daily for the duration of seven to ten days until the discoloration fades away. It can be repeated as and when required. However, patients with irritable bowel syndrome should avoid this treatment as pineapple has salicylic acid which can be harmful in this condition. 
It is advisable not to get panicky on seeing a black tongue as it is generally an innocuous condition. It gets corrected once the factors causing it are removed. One should try to practice healthy habits and lead a stress-free life. A physician should be consulted if the problem persists.