Black hairy tongue is produced when the papilla (finger-like projections from the surface of the tongue) fail to fall off as they normally do. As the length of the papilla increase, debris collects and bacteria grow, producing the characteristic dark "furry" appearance.
Review Date 2/27/2019
Updated by: Josef Shargorodsky, MD, MPH, Johns Hopkins University School of Medicine, Baltimore, MD. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.