Susan, this is the first time I ever heard the term "Eosinophilic gastroenteritis". I have no help to offer you, but I hope that now that the doctor knows what is making you feel so bad they can start to take care of the problem and get you better.
For the sore skin I have been keeping a bottle of lotion handy. After I cean up with toilet tissue I flush and get new toilet tissue and add a little lotion and wipe again. This cleans my skin and soothes it.
I also have a little sample bottle of lotion that I am carrying when I go out. Away from home cleaning with water is not usually an option....