Have a look on the Internet for Erythema Nosodum and
Pyoderma Gangrenosum, both can occur as a side effect of Crohns.
I got Erythema a few times, hospitalised once as it was so bad.
Has the doctor ruled out Psorisis ?, that causes red, scaly and itchy patches.
My brother has suffered from psoriasis for years, his was very severe and caused large raised scaly areas all over his body, and it itched terribly, he was recently put on
Humira and it cleared up completely.