Schnauzer skin problems - Could it be a heat rash?

by Jackie
(DFW, Texas)

Minni is our active 8-yr-old miniature schnauzer. She has a handful of medical issues that we deal with for her, but the one I'm asking about today is her scratching.

A few bits of info first: She has kidney issues -nearly died from kidney failure at four due to what the vet said was unknown poisoning- and is now on a special low protein diet prescribed by her vet. The food does have corn in it, but it's not like we can put her on any other food. We look in the stores constantly, but have found no substitutes. Her treats are easier: all hypoallergenic & vet approved.

We've also tried just about everything for allergies in the past: switching her diet (prior to her current diet) to eliminate all corn, grain, rice, and chicken, we tried her on organic food, we've used Benadryl, given her oatmeal baths, changed the frequency of baths (very often vs sparingly), tried vet-prescribed allergy medication, rubbed anti-itching cream/liquids on her back, and most recently have tried rubbing pure vitamin e on her back. NOTHING has worked. The only thing that lessens her symptoms is prednisone, but obviously she can't stay on that.

We do know she has allergies for sure, but we haven't had her tested. The one thing we do know is that even though the itching never stops year round, it's worst during the warm months. We don't allow her to stay outside long at all. -We live in Texas, so it gets hot here.- When she goes out in the daytime, she comes back with a super hot back that she can't stop itching. The vet said she thought it was allergies to pollens or grass, which I don't entirely disagree with, but there's a difference when the sun goes down. At night, Minni can be outside for as long as she likes. If we touch her back, she's still itchy, but it isn't overtly bothering her. Sometimes, bumps raise on her back, especially when she gets too hot, but they're temporary, not lasting more than a couple hours. -We put ice on her back when this happens, and it seems to help.

Is it possible that Minni has a never-ending heat rash? I can't find much information on mini schnauzers & heat rashes, so I don't know what I could do to help her if that's the case. The vet has been more interested in pursuing allergies as the culprit, but over the past few years, that hasn't panned out yet. Anyone have any suggestions that could maybe help out?

My thanks and Minni's to anyone who can help!