Why am I getting allergic reactions only in North America?

I have been having full bodied allergic reactions ever since I moved to North America. I come from a very polluted country in Asia with bad water and air quality and never really had any allergies. But ever since I moved here life has been hell. I have extreme eczema, hives, trouble breathing, wheezing, post nasal drip, tightness in my chest, watery itchy eyes and throat, and swelling.

I have moved houses, changed mattresses and air filters, nothing has worked. I have been to an allergist several times with no results. I test negative to everything(both skin prick and intradermal). I have been tested for both environmental and food allergies and every test has come back negative.

For a while they thought it was something autoimmune or immunological like lupus or MCAS. But last month I went to Europe and my skin cleared up with a couple of days. I didn’t have a single symptom during my time over there. I was equally stressed there as I usually am but I had no symptoms at all. My symptoms clear up everytime I leave America. I came back home yesterday and within 24 hours my symptoms are back. My eyes are swollen and red again and I am itching constantly. I don’t know what is happening to me.