When brick was a pup he devoloped demodec mange. I took him into the vet, and she stated that it was due to an immune deficiency. We agreed on Mitabin treatments. Its not a fast process, and your pup will look much much worse before he/she looks better. So its best to know that going in. Once the treatment starts. It kills all the active mites in his skin. Anywhere there was a mite, the hair WILL fall out. future treatments will be done to kill the new mites that have appeared from hatched eggs. Eventually, this will get rid of them all. the hair will slowly return, and your pup will look as good as new.
A side note about mitabin treatments. It does effect their mood. So be prepared for perhaps a bit of unusual crankiness, and if you have other dogs, a bit of snapping and your dog wanting an area to theirself for 4-8 hours after the treatment. After that they pretty much go back to their normal happy selves. We allways joked that brick was mourning the loss of his mites, and needed some "quiet time" lol. its nothing serious, Mitabin really does help. I think Brick ended up with a total of 6-7 treatments over a couple month span to get him free and clear.
Hope this helps.