I Went To A Dermatologist And He Took A Specimen

I went to a dermatologist and he took a specimen and the lab said it was a skin rash called exzima and now I have it again but I think it was from my Victoria secret bras because they have fermeldahide in them. I have not worn it in days but it's getting worse and I'm nnervous what's going on.
I have it behind my knees and on my ribcage . It's very itchy and looks like it's very dry and going to peel. I have been putting cortisone cream on it.