I'm not sure why I'm having an allergic reaction

Hi,

I am having an odd skin allergy and I don't know why. I know I am allergic to nickel, and to some powdered deoderants (like Secret and Sure), but nothing that I know of touched this area. It is between my breasts, and it's a similar reaction to nickel, where it's bumpy, swolen, red and itchy. Only, when I get a nickel reaction, I take off the nickel product and it is gone within a day. This I have had for a week and it's not getting any better. It started when I exercised 4 days in a row (I rarely ever exercise) and I wore an underwire bra. (I was only walking in place mainly - hardly brought a sweat) but I have read that sweat can leach the nickel out of bras and cause a reaction. I have exercised in my bra before and it has never caused an issue, plus, I did not get a reaction where the underwire is located, so I'm not sure if that's the problem, but it's the only thing I can think of.  I switched to a bra that had no underwire but the reaction still hasn't gone away (and I have not exercised since). It's beginning to worry me. Oh, and an important note: I do not have medical insurance and won't until the beginning of December. I will see my doctor then if it's still there, but until then, is there anything I can do to get rid of the allergy? What could I possibly be allergic to, just in that area??