I had sex with my partner a couple of weeks ago and a day or two later he complained of itchy red pimple like bumps on his groin area and testicles. He said this had happened before with a different girl he'd had sex with, and it was caused by my bacteria interacting badly with his own causing folliculitis. He started taking a topical antibiotic and applying that once every 8 hours. The bumps started to go away but keep showing up in different places (face, armpits, side, arms). It's not a colony of bumps just a few here and there and it seems once they go away in one place they show up in another.
The bumps on his groin area and testicles were almost gone and we had slightly rough intercourse using a condom. A day later he said his testicles were broken out with the itchy bumps again.
Any idea what this could be?
I have none of the above listed symptoms, it's just him. I also just recently got tested for STDs and all my tests were negative.