Black Hairy Tongue

BHT is a condition of the tongue in which the small bumps on the tongue elongate with black or brown discoloration, giving a black and hairy appearance. The appearance may be alarming, but it is a harmless condition.

Hairy tongue largely occurs in the central part of the dorsal tongue, just anterior (in front) of the circumvallate papillae, although sometimes the entire dorsal surface may be involved.
Discoloration usually accompanies hairy tongue, and may be yellow, brown or black.
Apart from the appearance, the condition is typically asymptomatic, but sometimes people may experience a gagging sensation or a bad taste
May Intra-oral halitosis

The cause is uncertain, but it is thought to be caused by accumulation of epithelial squames and proliferation of chromogenic (i.e., color-producing) microorganisms. There may be an increase in keratin production or a decrease in normal desquamation (shedding of surface epithelial cells).
Many people with BHT are heavy smokers.
Other possible associated factors are poor oral hygiene, general debilitation, hyposalivation (i.e., decreased salivary flow rate), radiotherapy, overgrowth of fungal or bacterial organisms, and a soft diet.

Diagnosis is usually made on the clinical appearance without the need for a tissue biopsy. However, when biopsies have been taken, the histologic appearance is one of marked elongation and hyperparakeratosis of the filiform papillae and numerous bacteria growing on the epithelial surface.
Hairy tongue may be confused with hairy leukoplakia, however the latter usually occurs on the sides of the tongue and is associated with an opportunistic infection with EBV on a background immunocompromise (almost always human immunodeficiency virus infection but rarely other conditions which suppress the immune system).

Hairy tongue (lingua villosa) refers to a marked accumulation of keratin on the filiform papillae on the dorsal surface of the tongue, giving a hair-like appearance.
Black tongue (lingua nigra) refers to a black discoloration of the tongue, which may or may not be associated with hairy tongue. However, the elongated papillae of hairy tongue usually develop discoloration due to growth of pigment producing bacteria and staining from food. Hence the term black hairy tongue, although hairy tongue may also be discolored yellow or brown. Transient, surface discoloration that is not associated with hairy tongue can be brushed off. Drug-induced black hairy tongue specifically refers to BHT that develops because of medication.

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