Black hairy tongue (lingua villosa nigra). Hairy tongue may also appear yellow, brown, white, green or pink due to retention of coloured food debris. Defective desquamation of the filiform papillae of the middle and back of the tongue result in hypertrophied and elongated 'hairs' up to 15mm in length. It may be asymptomatic or result in a tickling or burning sensation. Oral debris contributes to halitosis.

The papillae hypertrophy because they have not been debrided by the rough components of a normal diet. The discolouration is due to bacterial and fungal overgrowth. Predisposing factors may include: poor oral hygiene (lack of tooth brushing); tobacco use; excessive consumption of alcohol, tea and coffee; broad-spectrum antibiotics; psychotropic agents resulting in dry mouth; therapeutic radiation of the head and neck (lack of saliva and a soft diet); immune suppression especially due to HIV.

Refer to a dental hygienist if oral hygiene appears poor. Mouthwashes are ineffective. Treat candida if swabs indicate its presence. The patient should brush her tongue twice daily with a soft toothbrush or a tongue scraper. Keratolytic agents such as 40% urea solution, salicylic acid or tretinoin may be useful.