I get this after water exposure -- I call it my "after-shower torture". Anything touching my skin (like a towel or clothing) will set it off. It lasts about 45 minutes, but only if I can keep from scratching. I used to apply ice to the itchy spots instead of scratching. Also a good dose of Benedryll before a bath will nearly prevent it. And now that I am taking gabapentin the intensity is far more muted, and I can ignore the itchiness. It has made all the difference in the world.

Hope this info is of help to someone.
--Shari