Hi sorry to hear about your rash. Not many treating with interferon and ribavirin anymore since the new meds like Harvoni and Viekira Pak and now many others were approved since 2013 2014.
Curious where are you located that you were treated with interferon.
What advise has your doctor offered?
You may be able to find some help in the post hep c treatment community forum
http://www.medhelp.org/forums/Hepatitis-C-Post-Treatment-Issues/show/1670