What is black hairy tongue?

What is black hairy tongue?

Black hairy tongue is a temporary, harmless and fairly common condition in which the top of your tongue looks hairy. However, the substance on your tongue isn’t really hair and it’s not always black — it can be brown, green, white or other colors.

Little bumps on the top of your tongue — called filiform papillae — grow and collect food, bacteria and dead skin cells, which provide the color. The papillae are usually about 1 millimeter (1/32 inch) long and they’re supposed to fall off, like a layer of skin being shed, before they grow. This shedding process is called desquamation. If the papillae don’t fall off, they can grow as long as 18 millimeters (3/4 inch).