Well it seems we've lost the OP anyway.I hope I’m not pulling us too far from the original topic but the Feline Nutrition article really caught my attention because of the distinction between sensitivity (or intolerance) and allergy.
I think it is important that the vet know the distinction. I find it surprising that your vet would think scratching isn't a sign of allergy. I didn't know sensitivities can cause itching. I thought it was always a histamine reaction which only happens with allergies. But I'm not a vet.I agree with mschauer that the distinction isn’t as important as finding the offending ingredient, but after reading the article, I wonder if Lily would find some relief with an antihistamine.