why is my snot yellow

Yellow snot usually means that the body is fighting an infection. The yellow color comes from white blood cells that rush to the area to kill germs like viruses or bacteria. These cells, along with the debris they leave behind after fighting the infection, give the snot its yellowish tint. Yellow mucus is common during colds, sinus infections, or other respiratory infections and is a sign that the immune system is actively responding to the infection.