An overgrowth of the normal projections on the top of the tongue (papillae) can give it a hairy appearance. The overgrowth may be caused by food debris trapped in the papillae when people do not clean their mouth adequately. The tongue may also appear hairy after a fever, after antibiotic treatment, or when peroxide mouthwash is used too often.
These "hairs" on the top of the tongue should not be confused with hairy leukoplakia. Hairy leukoplakia is white, hairy-appearing patches on the side of the tongue that are a characteristic complication of AIDS.