In my 7 years-long search for curing it, I stumbled across many articles and stories, but I did not find any solutions. I read a lot about similar conditions — sun, cold, and stress initiated.
Mine was purely pressure related, but the solution I found should be useful even for those not pressure related.
The symptoms first appeared in February of 2010. One day the skin on my back suddenly started itching when I was sitting and leaning back in a chair and the more I scratched it, the more it itched.