How To Get Rid Of Dermatitis?

I have a rash... sometimes it burns and the doctors say its dermititis but they dont know from what? its all over my body...... except where my clothes dont touch.......... its on my face too but it comes and goes........ it itches....... alot........... and i can hardly stand it............. i have some food allergy symtoms too............ i cant use the creams they give me...... ugggggg...... help