If your mucus is gray or black... …you likely inhaled dark-colored particles, like smoke from a fire or heavy exhaust.

When a person has black or dark-colored mucus, they may have inhaled potentially harmful pollutants. Coughing up black mucus may also be due to an underlying infection or condition. Mucus serves ...

Julia Calderone wrote an earlier version of this post.

Black: This could be old, dried blood. The mucus can also turn black when environmental irritants, like dust particles, smoke or other air pollutants, get stuck in the nasal passages. Serious ...