How Should Dermographism Causing Facial And Torso Streaks With Marks Be Treated?

Hi, I suffer occassionally from dermographism and recently had a flair up. I scratched my face as well as my torso. The streaks on my torso have disappeared but the streaks on my face remain. Would exposure to sunlight have something to do with this and is there anything I can do to ensure the red marks disappear and don't scar (which I suspect they have)? Many thanks.