I have a recurring blister-like rash on my index fingers and, occasionally, my thumbs. There are many tiny bumps, about a mm thick, filled with clear fluid. There is severe itching and a burning sensation, releived and aggrevated by scratching. I've been given hydrocortizone and piriton but they do little to help the problem. The itching is only briefly releived by pouring very hot water on my fingers. What can this be?