
Firstly, Guest, please register as a member :) We don't bite...might growl a little sometimes but never bite ;)
You need to try to determine what is causing the skin condition. There are any number of factors that could be at the root of his problem. Commonly an intolerance to some ingredient in food (corn/maize is a problem for one of my dogs) or an allergen in the environment (dust mites, grass, household detergents etc) can cause these type of symptoms. There is no point in trying to treat the symptoms if he is continually exposed to whatever is causing the irritation.
What breed is your dog? Has your vet had him tested him for allergies or tried him on an exclusion diet? What food are you currently feeding? What do you wash his bedding with? Which anti-histamine was he given? Could you ask the vet for a different brand? Skin conditions are notoriously difficult to diagnose and treat and it can take some time with any particular course of action for improvement to become evident.
Sorry that there are more questions than answers...please join so we can try to help :)