Zyrtec's skin problem
I went through similar with all 3 of my skinny pigs. I now have 2 more. For 2 years or more I tried EVERYTHING. I ended up getting a skin biopsy. It ruled out mites, fungus, etc. I hate to think of how many times I tried treating for mites & fungus. In the end it came down to 2 main things for us... humidity and diet. When I finally checked with a hydrometer (thanks, I think to Lynx's suggestion) I was horrified to learn my humidity was at mid 20s, and this was with running an ultrasonic humidifier 24/7. When I got it up to 40-50% things got better. On my pigs a scaly, scab-like patch on the back would come and go. I noticed it seemed to coincide with my feeding them any green other than lettuce. So, I'm talking grass, parsley, cilantro, artichoke, corn husk, you name it. When I stick to green leaf, red leaf or romaine (rarely) lettuce only, we have no more scab-like dry patch. Also, one of my new rescuces came with a skin issue. It started to clear immediately with better diet. I would attribute it mainly to better pellets. I use KMS.