
What colour is he? Dilutes (blues + fawns) usually have coat problems, blues especially, and these little bumps are often seen.
It could also be a staph infection (afraid I don't know much about those, but they are common in pups, causing bumps and itchiness). The best advice I could give you bar none is to go here:
http://www.network54.com/Forum/11341
It's the best dobie message board I have come across, and the members have helped me with every issues I've had with my fawn male. Get yourself a membership, and post your problem there - I have no doubt they will know what it is!