How do I know if I'm allergic before I spend money on latex?

I have wanted a latex piece for ages but I keep talking myself out of it, because I have no idea whether my skin will hate it. I get itchy with some plasters and cheap earrings, so now I am nervous about spending real money.

Is there a sensible way to test this before I order something expensive? I would feel silly buying a whole top only to break out in five minutes. Do people do a patch test, and if so, with what? And is a latex allergy the sort of thing that gets worse each time, or is a bit of redness just normal when the material is new to you? Any calm advice welcome.