I am in no way qualified to give you an opinion, unfortunately (fortunately for you, though!)
Perhaps you should place two separate posts under the Tykerb/Herceptin board. One under the" Please list all side effects of herceptin real or imagined"
thread and the other as a new thread. If you get no answers, I would suggest coming back to the her2support board and starting a thread asking whether others have had skin rashes which persisted more than 4 months after stopping herceptin (and more than 10 months or more after TC treatment)
Is the rash in an area that was radiated? If so, the following might be helpful
http://www.cmaj.ca/content/182/3/E150.full http://lungcancer.about.com/od/radia...ion-Recall.htm
Good luck with getting help...there are many here with lots of personal experience