Maggot infestation

Of all the freaky medical conditions out there, one is most disgusting. A team of researchers at the Hygiene Center at the London School of Hygiene & and Tropical Medicine conducted a survey in 2010 to discover what medical conditions humans are most disgusted by. They presented 20 images of things perceived as repulsive from festering wounds to discolored bodily fluids to more than 80,000 individuals from around the world, and had them rate the images from least to most disgusting. 

The image universally ranked as most disgusting is what you see above the mouth of a man who suffers from a Sarcophagid fly larvae infestation. 

This medical condition ranks as most repulsive, said lead researcher Valerie Curtis, because "disgust is designed by evolution to keep us away from parasites that may make us sick, so people pick up on, and are most disgusted by, visual representations of a parasite invasion."