lab work

My father has a 5 year hx of waxing and waning red raised rash to his upper arms and upper thighs which worsened recently with crusty bumps and intense itching.  He has a history of chronic plaque psoriasis which is on the knee and elbows only.  The rash was biopsied and showed spongiotic dermatitis.  Prior to this biopsy diagnosis, treatments had included Bio-Fen, Clobetasol, Triamcinolone, and Derma-Smoothe/FS.

His doctor has ordered the following blood work:  CBC, Hepatic Profile, Protein Electrophoresis, Renal Profile, Serum Porphyrins, serum tryptase, serum IgE and IgE receptor autoantibody?  Is he looking for a systemic cause of the rash and what might this lab show?