I Developed A Rash 4 Days Ago After Camping. It

I developed a rash 4 days ago after camping. It started in my arm and has progressed to my chest, hips, face, hands and thighs. I started prednisone 3 days ago and it seems to be spreading more. My face is also swelling a lot too. It doesn't seem like poison oak because the rash is very semetrycal. I'm starting to get concerned. Any thoughts?