This reminds me of my first encounter with crabs in Southsun. I'd get the thing on my head, and notice there was a condition. Mousing over it would inform me that I had a crab on my head. Terribly useful there. It was a complete mystery. I figured it must have some effect other than just visual and that condition that didn't seem to mean anything.
It took me quite a while to realize that the crab was applying other, more standard conditions, but because I was playing a D/D ele I was cleansing them off so fast as a normal part of my rotation, that all that was left was the headcrab condition.