A homeopathic remedy worked very well for my son many years ago. It's called Rhus Tox. It stopped it in its tracks. However it did not work for me.
When I had severe PI on my hands I used a combination of Aztec Healing clay, found in the health food stores, wetted with some apple cider vinegar. It completely arrested the itching as soon as it was applied. It took several days to finally leave but I was happy to know that a remedy existed.