Maggie...
So sorry your son has to deal with cancer but the Tarceva has helped me.
I got the rash in 8 days & was given a scrip for Clindamycin Phosphate Gel usp, 1%.
It helped a lot & it could work for your son. I have periods when the rash goes away & then it will come back again but seems to be less bothersome each time.
Hope this helps....God bless.....Connie