I am updating my article on the usefulness of the SDMA kidney test.
If your vet  has followed SDMA levels in your pet, perhaps you would 
share those values with me. RSH email
I copied a portion of the chapter on skin testing procedures for allergies from my copy of the 2001 edition of Muller and Kirk's Small Animal Dermatology. It is quite hard to read, but you can view it here.