It's probably not an allergic rash, per se, but just a skin reaction to the Ribavirin. I would call the doctor and ask about it. Some of the things that help: stay moisturized, don't take hot showers, pat your skin dry, use a moisturizer, drink lots of water. You can ask your doctor for a prescription called Hydroxyzine and an ointment called Triamcinilone to see if those help with the itchiness.
A PCR is the viral load.