I Have A Severe Itching, Not At All Times. We

I have a severe itching, not at all times. We have tried changing soap, softner, detergents, shampoos, tracked what I eat and drink, everything we could think of. It happens all over my body. Even if I have even a slight itch and scratch it, it spreads, I break out in hives, big welts. Only thing that helps even a little is Benadryl gel and apply several times. I have scars from scratching all over, except my face and neck. Mostly feet and legs, and arms. It happens mostly at night. When I was a kid I broke out in hives/welts from Penicillin, have'nt taken that in 50 years.I am Diabetic, on Metformin. Thank you.