I've been on Erbitux for some time (about 12 weeks now). My rash seems to 'move' every couple of weeks. I'll have it on the face, then my chest, then my legs, then my scalp, etc.
My doctor had me try T-GEL shampoo and it has worked remarkably well. You have to keep it moist though as the T-GEL and similar products will dry you out if you let them.
-steve

Age 41 - Stage 2 SCC tongue Dx 2/06. Cisplatin x3, IMRT x35. Mets to neck node discovered 7/07. RND 40 nodes removed, margins not clear. Cisplatin, Taxotere, 5-FU Fall 07, then IMXT/Erbitux for 7 wks. Inoperable mets to both lungs and pleura Dx Oct'08. 4 cycles Carboplatin, Erbitux, 5-FU so far.