I completed a year of Herceptin IV treatment given every 3 weeks for HER2+ cancer. After my breast surgery (right side) I noticed my right arm itched all the time. First I thought it was bug bites causing the itch. Finally my internal medicine doctor looked at it and treated it as a neuropathic itch and prescribed gabapentin. The gabapentin helped significantly the keep the itch under control. I noticed the itch was much stronger the week after my Herceptin treatment. Once I finished my year of treatment I tapered off the gabapentin and the itch has never come back! This is not a known side effect of Herceptin according to my doctor however my sister also had breast cancer and had the same side effect!