What Causes Penis Glans Rash With Itching?

I have a red rash on my knob and it itches alot, im just wondering what it might be from. Its been there for maybe a week now. I have been taking anti biotics for 5 days and just finished my medication. I was taking the anti biotics due to a throat infection, and i have been having sex for about alittle over a week every night, not sure if that might be the reason.