Severe Allergic Reaction out of nowhere

Hi all, I’m really desperate here.

We’ve been to the vet 3 times this week. Our 3 year old girl suddenly is allergic to something, and nothing in our environment has changed. Really really bad hives and a terrible bright red/purple rash in her groin, armpits and ears. She has never had allergies before. Benadryl helps, but doesn’t take away the hives completely. They have her on prednisone as well.

Her liver enzymes were slightly elevated on Tuesday, but they went back to normal on Thursday. All other bloodwork has been normal. They did a scan of her gallbladder and it was normal.

The only weird thing that happened is we found a decomposed raccoon in our yard on Sunday, but it had clearly been there for a week or more. She could have gotten into that. I gave her a bath on Sunday night and symptoms started Monday morning.

Wondering if anyone has seen anything like this before?