What Causes Itchy And Bleeding Rashes On The Arms And Legs?

My husband age 64,has had an itchy rash that will bleed because of all the continuing itchy, which can be server at times. It s mainly on his back his legs and arms and has had it for over 2 years. The Dr keeps giving him a topical cream which can slow the itching but is not treating the underlying problem. We have tried different soaps, different shampoos, laundry soaps, oatmeal wash,everything. I just thought tonight about possibly being deficiency in a certain vitamin that might cause this problem. He is in really good health, is 6ft , about 190 lbs. He is under a ton of stress though, he is in the home building business, a home designer and contractor. This problem started over 3 years ago during the down turn of the economy, but got severly worse since then with the last two years being the worse. Any thoughts on vitamin deficiency ?