I was born with a penicillin allergy. Every time that I have ever taken Bactrim DS for a UTI I have experienced itching in my genitals, but I just thought that was normal because the medicine was fighting off the bacteria in my nether regions. Was that an allergic reaction? Also, the past 2 times I have taken Bactrim DS I have developed a red rash on my face in the same places, what does that mean? Could I have been born with an allergy to Bactrim/sulfa medications?