Your sister developed POST HERPETIC NEURAGIA, the medication GABAPENTIM will stop the itching,usualy it takes 3/4 days after starting with the medication to stop the itching .Some people can stop gabapentim after months,others years,other wont be able to stop ever. Despite is an epileptic drug is used to treat Post herpetic neuragia.I take 2 gabapentim before bed time.What my doctor explained to me is that the brain keeps sending signals of itching,some people feel the pain after cleared the shingles, and because some nerves were damaged due the shingles the brain keeps sending WRONG SIGNALS, the gabapentim will stop the brain to send the signals to the body(some people itch, others feel pain,others have a burning sensation). If you search a bit you will find thousands of people that had their problem solved with Gabapentim,It will take 3/4 days for the medication to kick in and stop the itching,her life will improve 100%.Good luck
sorry i posted your sister, i meant to say YOU,It's because many people asked the same question about the itching ,then i wrote just one answer to everyone that asked about itching relief.
I wonder if menthol muscle gel would help... I use it on my face when my rosacea itches. I also have to avoid high arginine foods ((anti-)herpetic diet), like avoiding nuts, seeds, caffeine, chocolate, etc) to reduce the inflammation flare.
Ohh, I've also tried peppermint oil but not as much success as the menthol. Avoid contaminating your containers... and AVOID contact with eyes with anything you try on your face. Wash hands after touching inflamed area. Keep us updated with any success you find.