Do not miss Golob's wonderful piece about wonderful snot:

Snot is your body's best defense mechanism, a sticky moat of protection against invading bacteria, viruses, and fungi. When it comes to where your body is open to the outside world, snot (more properly, mucus) provides a barrier against these alien invaders.

Later in the column:

As the outer layers of snot are eaten or rubbed away, new layers are forming underneath—creating a sort of treadmill of slime for invaders to run on. Hence, during an infection, our bodies tend to make more snot in an attempt to run the invaders out.

Although the surplus of snot is not much fun when we're sick, it's better than the alternative. People with cystic fibrosis have a damaged chloride receptor, preventing them from properly filling their snot with water. Without the nice slick snot, people with the disease are subject to all sorts of terrible infections—particularly in their lungs.

Mucus is disgusting because your body's enemies are disgusting.