Skin dryness in northwest, but not in desert, no allergy medicine helps?

[Annoyedanditchy]

Hello, I have a question about dry skin occuring in very specific spots and in what appears to be any environment other than a desert. Any help would be very, very much appreciated. I'll start with a bit of a background:

I am 28, female, no children, I do not smoke or drink (and never have), I also do not drink caffeine. I exercise regularly and eat healthy. I have GERD,  vulvodynia and hormonal migraines. I take zantac on a daily basis, and used to take Benadryl dailly for years. I take Imatrex generic as needed, about 4 half pills monthly all within my period week and rarely one around ovulation. I also use a lidocane gel as needed for the vulvodynia.

I use natural laundry detergent and shampoo and use cetaphil and aveeno unscented lotions.

Not too long ago I was living in the Northwest United States, I grew up there, and when I was 18. I started having itchy skin issues. I tried *everything* to treat it over the years. From humidifiers, to hydrocortisone, to every natural and fragrance free lotion, cream and balm out there. The symptoms changed a bit through the years, and seems to have two "forms". One was a rash in patches. Mostly on the inside the bends of my arms, sometimes on the outside near the shoulder and occasionally on my neck. The other form, that is the most persistent today, is a dry flaking and peeling skin, specifically on my eyelids and nipples of all places.

The patchy rashes on my arms and neck actually respond to allergy medications (usually) like benadryl, however the dry scaly flaky eyelids and nipples do not. In fact they don't respond to much at all, just cetaphil can mask the itch and pain for a little while. Even then it can burn the eyelids sometimes.

While living in the Northwest I did see a specialist for my condition, and while he had no explanation for the skin trouble he prescribed something (prednisone I think) for my arm and did a biopsy at the same time which came back normal. The prednisone worked for my arm rash that was persistent at the time and it never came back. After this I never had the arm rashes again, actually. However the medication was too strong to use on delicate places like eyelids and nipples, so I was stuck to a high percentage hydrocortisone for them, which did nothing at all. And all the while I had been trying every other over the counter treatment for the condition, fish oil, vitamin a and e, natural lotions, everything frangrance free, eating healthy, allergy medicines (every otc brand out there. I generally gave them a couple weeks to see if they had any effect) and all to no avail.

Now where things get interesting is we moved to Arizona a couple years ago and since moving here within a week my dry painful eyelids and nipples (that I had for 8 years constant) were healed! For over a year I barely needed lotion, let alone the slathering I gave them several times a day in the Northwest. I felt human again.

Recently we traveled to Europe and while there my skin erupted, it was nearing intolerable, again it was only the eyelids and nipples. My eyelids get so scaly and inflamed I can't open them all the way sometimes, and my nipples literally peel a new later of skin completely off every day when this happens. I itched until I bled. I want to make it clear it is just the nipple that itches and peels and not the areola, that does not get flaky at all. All the while I was taking benadryl daily and it didn't help, it was JUST like living in the Northwest again. Then when we came home to the desert it took a few weeks for things to settle down but now I am barely itchy and overall feel great and am not taking any allergy medication anymore. (first time in probably 5 years!)

My question is, why is this happening? If it were just allergies, wouldn't allergy medication help? It helped with an arm rash I had, but does not help with the eyelids or nipples in any noticeable amount. I don't necessarily want to live in the desert forever, but as it stands now I don't know if I would have much of a choice as it seems to be the only place that my skin is happy, despite the low humidity. Is there a test I can do to find out why my skin reacts this way and to what? And if benadryl, allegra, zyrtec and Claratin all didn't help, is there anything that could? Please, I want to understand why my body is doing this.

Thank you