I can completely relate, CMdeux! I find myself realising how many allergic reactions I've had that I thought were asthma and I get scared. It's only afterwards that I realise that it was probably an allergic reaction and not asthma. Even for the person experiencing it, it can be very difficult to tell the difference. The biggest thing I notice (in retrospect, and I'm trying to get better at this), is throat swelling. Even just the tiniest bit of throat swelling is Epi for me, but it can be easily mistaken for low-grade wheezing or chest tightness, and that's what gets me every time. Too many times. Add in some panic and fear, and it's just a really bad situation to be in.
Two months ago I drove myself to the fire department (I was in my car, two blocks away at the time) because I had one of these undetermined reactions that wasn't responding well to Salbutamol, but by the time I got there it was starting to resolve itself and they just monitored me for a while. (Our local firefighters are also advanced life support paramedics.)
This is a question that may not really have an answer, and I hope one day that this will be talked about with more certainty. On the safe side, I think it's better to Epi than not, especially with a history of super sensitive allergic reactions: aerosol, contact, traces of traces, etc. Now, if only I could get my brain trained to think like that...