Black hairy tongue is a temporary, harmless oral condition that gives your tongue a dark, furry appearance. The distinct look of black hairy tongue usually results from a buildup of dead skin cells on the numerous tiny projections (papillae) on the surface of your tongue that contain taste buds. These papillae, which are longer than normal, can easily trap and be stained by tobacco, food or other substances, and bacteria or yeast.
Although black hairy tongue may look alarming, typically it doesn't cause any health problems and is usually painless. Black hairy tongue usually resolves without medical treatment.