Fissured tongue is a normal variant of tongue appearance and is not considered a pathological entity. It generally presents in healthy people; however, it is also seen in association with conditions such as Down's syndrome and geographic tongue. If the sole manifestation is that of fissured tongue, then no investigations or treatment are usually necessary.
Hairy tongue occurs when the physiological balance between keratin production and shedding through normal oral function is chronically disrupted with consequent elongation of the keratinised component of the filiform papillae that cover the tongue dorsum. Poor oral intake during illness or oral discomfort secondary to oral ulcerative conditions are examples of situations where physiological keratin shedding secondary to mechanical debridement may be reduced. Smoking, coffee or tea, or poor oral hygiene are examples of predisposing factors.
Improving oral hygiene, stopping smoking, and using a tongue scraper appropriately aids management of hairy tongue.
Geographic tongue appears as well-demarcated red areas of the dorsal and lateral tongue, with white scalloped borders.
Its aetiology is unknown and no treatment, other than symptomatic relief, is generally necessary.
Fissured tongue is a common, benign clinical condition of unknown aetiology usually affecting the dorsum of the tongue.  On physical examination, numerous grooves or fissures are seen on the dorsal surface of the tongue; these are usually a few millimetres in depth. They may occur in isolated areas of the tongue or may cover the entire dorsum.
Hairy tongue is a common, benign clinical condition with the hairy appearance on the dorsal tongue caused by keratin retention on the top of the filiform papillae. Hairy tongue presents on the dorsal tongue as diffuse hair-like projections especially in the midline of the dorsal tongue. The colour of the elongated papillae may range from yellow to brown-black. There may be a difference in the colour of the elongated papillae due to the exogenous staining from different foods, tobacco, and chromogenic bacteria. 
Geographic tongue is a common, benign clinical condition that predominantly affects the lateral margins, the tip, and the dorsal part of the tongue. Rarely, it may occur at other sites within the mouth, such as the buccal mucosa, labial mucosa, and soft palate. Geographic tongue presents as well-delineated areas of erythema with raised white circinate edges. 
Consultant Senior Lecturer in Oral Medicine
School of Oral and Dental Science
University of Bristol
KSS declares that he has no competing interests.
Dr Konrad S. Staines would like to gratefully acknowledge Professor Aisha Sethi, the previous contributor to this monograph. AS declares that she has no competing interests.
St Mary's Hospital
Imperial College Healthcare NHS Trust
NOD declares that she has no competing interests.
Professor of Oral Pathology
Head of the Department of Oral and Maxillofacial Surgery and Oral Pathology
VU University Medical Centre and Academic Centre for Dentistry
IVDW declares that he has no competing interests.
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