Hints for helping an obsessive 4 year old?

I have a 4 year old son whose face I can't seem to get to heal. What started off as an insect bite on each cheek has turned into a series of sores that he constantly stratches and re-opens. He also has been tearing at the bridge of his nose, right between his eyes. His chin has also suffered at times, but is currently clear (it only took a month to get that way). Keeping bandages on him is helpful until he developed a latex allergy which caused the bandages to leave a painful, scabby rash, which he also picked at. I now keep paper tape (hypoallergenic) over his trouble spots, but if they come off during the day or I forget to apply the tape, we have to start over at square one. The spots on his face are going on 8 weeks now without healing. I think they are healed, I stop putting tape on his face, and presto, they are back. I know he inherited the trait from me. For me it was always a stress reaction and when I was at my worst it was my forearms that bore the brunt of my obsession. Leaving the job that was causing the stress allowed the problem to subside enough that it ceased to be an issue for me. But my son is 4 years old. He doesn't have a job to quit. I'm looking for a new daycare provider, and I'm wondering if stresses with his current baby sitter isn't making things worse (he doesn't say much about her, but there are things that have made me think I need to replace her). Does anyone else have children who engage in this behavior? Besides keeping the spots covered, does anyone have any advice to help the child deal with the compulsion? I know he can't help it (I don't just know, I understand that he can't). I just want to know if 1) I'm the only parent of a child this young who does this and 2) if anyone has any tips or ideas beyond what I've described. Thanks, all.