Can Bactrim Cause Allergic Reactions?

I have taken 3 Bactrim, two yesterday and one today. Tonight as I was working I began itching and it got worse and worse and when I looked I have red whelps all over my body that burn, itch and sting. They are on my abdomen, back, armpits, groin and pelvic area. I have a wisdom tooth that is swollen and hurting and that is the reason I took the Bactrim (the wrong thing I know but it was my daughter's prescription that she did not complete). Does this sound like a reaction to the Bactrim? I have some OTC Benadryl but have not taken any. I sprayed it with Bactine with some relief but not for long.