I scratch at my scalp as well... I think for me it's a nervous thing, sometimes it bleeds. I've had to sit on my hands before to stop myself from scratching.
I don't know if it's a form of SI.... but I know for me it's a nervous thing.

<font color=red>~</font color=red><font color=blue>S</font color=blue><font color=green>u</font color=green><font color=blue>n</font color=blue><font color=green>d</font color=green><font color=blue>a</font color=blue><font color=green>n</font color=green><font color=blue>c</font color=blue><font color=green>e</font color=green><font color=red>~</font color=red>

<font color=blue>"Never react emotionally to criticism. Analyze yourself to determine whether it is justified. If it is, correct yourself. Otherwise, go on about your business."</font color=blue>

<font color=black>Norman Vincent Peale</font color=black>