I have not had a skin biopsy but was diagnosed with SFN. Last year beginning in May I started to itch and it began on my scalp. It would spread to various parts of my body. I thought I was going to go bonkers. My allergist, dermatologist and primary had me running in circles. I spent so much money on various OTC remedies- nothing helped. I've had blood work for systemic and auto immune- negative. Allergy tests- negative. I was even tested for parasites and fungal infections. I am being tested for Mast Cell Activation Syndrome currently. Benadryl took the itch away but I was a zombie all summer- lost months to this extremely horrible itch. I take Zyrtec now and I think it helped but mine seems to get bad with heat and humidity, so I won't know for sure until summer.