
It certainly sounds like an allergic reaction. The problem is to identify what he is allergic to - it could be food, insects, household cleaners, tobacco smoke....the list is endless. There are tests your vet could run to discover what it is (intradermal skin test, or RAST).
I would have thought with his smooth coat a good brushing each day would get the dust out of his coat. Otherwise would just rinsing him in clean water after a brush be adequate?
Hope it sorts out soon. :)