I just found out I’m allergic to coke. What makes me special?

I’m in my late 20’s and have done coke maybe 6 times. I never had a reaction until about 4 weeks ago. I had a drink and a pill, so it could have been either, but my face got really hot, my eyes turned into little slits and my skin turned red and was itchy. This subsided quickly, but I still feel uneasy about it bc what’s going on in my body?!<br><br>I’ve had other vices on a regular basis that I’ve always been fine with. <br><br>Am I allergic to coke because I have small pupils? Is it because my heart is large and strong?<br><br>Please give some insight if you have a medical background.