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 Epstein–Barr virus on a background immunocompromise (almost always human immunodeficiency virus infection but rarely other conditions which suppress the immune system). Classification 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. Treatment Treatment is by reassurance, as the condition is benign, and then by correction of any predisposing factors. This may be cessation of smoking or cessation/substitution of implicated medications or mouthwashes. Generally direct measures to return the tongue to its normal appearance involve improving oral hygiene, especially scraping or brushing the tongue before sleep. This promotes desquamation of the hyperparakeratotic papillae. Keratolytic agents (chemicals to remove keratin) such as podophyllin are successful, but carry safety concerns. Other reported successful measures include sodium bicarbonate mouthrinses, eating pineapple, sucking on a peach stone and chewing gum. Prognosis BHT is a benign condition, but people who are affected may be distressed at the appearance and possible halitosis, and therefore treatment is indicated. Epidemiology Hairy tongue occurs in about 0.5% of adults. However, the prevalence is variable depending on the population studied. References External links Tongue disorders Conditions of the mucous membranes