I was prescribed Bactrim DS for what was either a spider bite or ...

I was prescribed Bactrim DS for what was either a spider bite or cellulitis. I have been taking it for 8 days out of the 10 I was told to take it. I will not be taking anymore of this horrible stuff! Just a s few hours ago, I took the last pill. My arms are now covered in bright red spots. And my eyes are red and itchy. I have NEVER had an allergic reaction to ANY medication before, so I didn't think I would have one to this. I hear it is the sulfer that people are allergic to. If you are prescribed this stuff and you aren't sure if you are allergic, I strongly suggest you not take it.