Dietary regimen symptoms and conditions

I was prescribed Sulfameth for an inflamed cyst on my back. It was a 10-day prescription. The first symptom a few days after starting was unusual fatigue. This was followed by severe itching on my feet, though initially I didn't make the connection between the itching and the antibiotics. This itching then moved to my testicles, and the day after the prescription was finished I noticed redness on my testicles, small red splotches on my penis, and a large red splotch on my left elbow. At first I thought it was psoriasis, but I have no history of that and the only change in my usual physical/dietary regimen is the Sulfameth.