Something other than Reta?

I started Reta around a month ago. I am on the lowest dose still (.25). I went up to .3 for one dose. Within hours of injection, I have what seems to be a shingles outbreak in my buttocks area (crack to be specific). I can’t handle it. It’s painful and very itchy. Is there something else I can take that doesn’t have this side effect? Has anyone else experienced this? Will it eventually stop if I continue? I have lost around 8-10 lbs since starting, but I can’t tolerate my skin problem now. TYIA.