I am allergic to bactrim and my husband was prescribed bactrim to clear up an infection from a spider bite.  While he was on the medication, we had sex and the next morning, I had the rash over my chest like I had previously gotten when I took the Bactrim.  Anyway, he has ben finished with the meds for over a month now, and I am still breaking out in the rash after every time we have sex.  What could be still causing this.  We have been married 11 yrs and I have never had any allergic reaction to him.
Well, if you are allergic to Bactrim and your husband got treatment with Bactrim, and you had sex, it doesn't cause allergic reaction to you on having sex with him. Such cases are not reported in my knowledge. This could be a co incidence or reaction with something else. Better follow all the instructions of your treating doctor instead of guessing. To my own patients, I would have given safe herbals to manage it. HARD Chat Doctor. Hope it helps you.