Why is my mage "sweating blood"?

I'm about 12 hours into Dragon Age Origins for the first time.

During most of the game, my mage has been sweating what appears to be off-colored blood. My daughter explained that this indicates I've killed humans.

However, the graphics has disappeared for periods of time only to return later in the game.

What does the "sweating blood" graphic mean and how can I make it go away (in game and out of game)?