Allergic reaction to antibiotics or Syphilis rash?

I have a rash after taking this antibiotic that apparently I'm allergic too because I had all the side effects mentioned on the handout. Anyway, I went to the doctor and she thinks it might be a syphilis rash. The rash is on my torso, neck and head. It's very itchy. I read about syphilis rash and that rash is not itchy and besides the syphilis rash is supposed to be on the palm of the hand and on the foot. Mine is on the torso, neck and under my hair. What are the chances that it could be a Syphilis rash?