Zeraph

Bacteria or mold isn't going to grow in it but it may have a virus (unlikely) in it from outside exposure. I was thinking more along the lines of a bad batch, like it got too much of some chemical in it (unlikely though).

More likely you're just sick, and aren't feeling it or maybe dehydrated. There's also a slight chance you've grown allergic to one of the ingredients. That can happen, even down the road, at 25 or 30 you can suddenly become allergic to shellfish for instance. Although I'm not sure I've ever heard of someone becoming suddenly allergic to a type of liquor. Beer or wine, yes. For instance, I don't throw up, but I get pretty nauseous on the majority of beer or wine. Whereas I can do 4-5 shots in an hour and be fine.

I'd give it another day, if you still feel fine, then try a shot of something else. But I'd start thinking about seeing a doc if I were you (if you have the insurance or the symptoms get worse). It's possible it's indicative of something a lot more serious, but I'm fairly paranoid about this stuff.

The last possibility in my mind is your body just conditioned itself because the last time you drank was too much. I've known plenty of people that drank too much of rum for instance, and just the smell of it makes them nauseous.