After they’ve done their job and die, they’re flushed out of your body with your mucus, and in the process can dye it yellow. Yellow mucus doesn’t mean that you need antibiotics, but it ...

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

Does Green Mucus Mean Infection? Green or yellow mucus can sometimes signal an infection. Bacteria and viruses cause inflammation in your nasal passages, leading to excess mucus. A sign that an ...