acne
"I started on trimethoprim after taking a variety of different antibiotics for several years including erythromycin and lymecycline. 
I have been taking trimethoprim for three months now, and have halved my dosage after seeing an improvement. 
My skin has remained relatively clear (bar one or two spots) and I presume there hadn't been a growth of resistant bacteria since my skin has not worsened after lowering the dose (unlike other antibiotics I have taken). 
I'm giving it 9 because I haven't gone off it completely yet, and don't know what the result of that would be."