You can't rule out an allergic reaction based on the fact that you have taken something before without a problem. You can develop an allergy to something that you've never had a problem with before at any point in your life. A good example of that with myself is aspirin; I took it most of my life without a problem but in college developed an allergy to it (breaks me out in hives every time I take it or any medicine with aspirin in it). Same thing with a couple of antibiotics; never had a problem with them until I was over 20 and now I'm very allergic to them.
Now that you know that you react badly to a normal dosage, though, you can be cautious the next time you need it and either find something else or take less of it.