Mold allergy?

My 9 yr old male dachshund is having his 2nd bout with what appears to be a pretty severe allergic skin reaction.  He rolled in my parents yard and subsequently went bumpy from next to hind quarters; bumps that fairly quickly turned to scab (like) that took the hair with them when they fell out.  Our country vet diagnosed yeast/mold allergy and suggested 200mg Ketoconazole once daily and a bath in Nizoral with a vinegar and water rinse.  That worked for round one, but almost as soon as his pills were gone, the bumps came creeping (literally) back.  He awoke this morning with almost as many bumps as he had when this started 3 weeks ago.  Is this illness likely going to require continued use of the Ketoconazole pills?  They make him woozy, sleepy and extremely thirsty.  Is there anything else that I can do?  If this came from his roll in the yard, have any of you heard of an effective yard treatment worth trying?  Thanks for any help.  I hate seeing him so uncomfortable.

[ginger899]

The simplest solution may be to stop him rolling. I know it doesn't solve the allergy problem. But it will solve the problem repeating itself every time he goes there.
I know it will be hard to stop him, when I guess he just rolls because he always has done. But it would be possible to stop him doing this.

Before a roll, dogs usually sniff the ground, then start to position themselves head down. If at that point you catch him, and snap him out of it with a firm "NO" (don't yell, do not be annoyed, just be firm. Even give him a quick nudge on the shoulder) If every time he starts this and gets the same from you I can guarantee he will stop doing it very quickly.
That's the best solution I can give.
There will probably be other ideas for this problem, from others here, so watch this space....