A yellow, furry tongue is sometimes a sign of a condition called black hairy tongue, according to Mayo Clinic. This condition may result from antibiotic therapy, poor oral hygiene or tobacco use. In rare instances, a yellow tongue is a sign of jaundice, which indicates a liver or gallbladder problem.
Black hairy tongue is a harmless medical condition that is characterized by a hairy or furry appearance of the tongue, metallic taste in the mouth, bad breath, gagging sensation and a black, brown, tan, green, yellow or white discoloration of the tongue, states Mayo Clinic. It generally happens because dead skin cells build up on the papillae, which are tiny projections on the tongue's surface. This causes the papillae to lengthen and trap food, tobacco, bacteria, yeast and other substances that discolor the tongue.
Black hairy tongue is generally resolved easily with good oral hygiene, according to Mayo Clinic. To remove dead skin cells, food and debris, the tongue should be gently brushed whenever teeth are brushed. It is best to use a soft toothbrush or a flexible tongue scraper to clean the tongue. Teeth should be brushed at least twice a day and flossed at least once a day to remove food particles and plaque from the mouth.