My problem is just above the knee, first it was a very bad itch , I started to scratch uncontrolably , and the next day it was very swollen , and now it has a little pus coming out right in the center ,with a bit of blood , and my skin on top is very thin like a sheet of plastic, help please

Well I'm off to see another rheumtologist tomorrow - though not very optimistic that it's going to bring up anything new... Will let you know if he has any ideas...

Well I'm off to see another rheumtologist tommorrow - though not very optimistic that it's going to bring up anything new.... Will let you know if he has any ideas....

What does this have to do with the OP?

Bug bite, spider bite, poison ivy or oak or sumac, who knows without seeing it? Wash it and apply some cortisone cream available at any drugstore. If it spreads, ask back.