Sick 7 year old

I have no idea where to post this question so here I go. I have a 7 year old who has bouts of diareah and headaches for the last year. Only recently she started getting blister(with no liquid) on the end of her fingers and within a few days her hands were peeling and cracking and feel very leathery. A few days later this spread to her feet. The skin turns white and then falls off. The doctor suggested maybe autoimmune but then instead of testing her for anything just perscribed cortizone cream. I am thinking maybe an allergy but I don't know. She is also slim but eats like a pig but she is very active. There is a history of pituatary growths in our family and also diverticulitis.HELP