What Causes Red Rash With Itchy Skin On The Head Of Penis?

I had sexual intercourse with my wife 2 nights ago and yesterday when I woke up I had a red rash on the tip of my penis and my foreskin is red and very itchy. I normally wash afterwards but I didnt and my wife washed just before. Is it possible that she left some soap inside and caused a rash as she is slightly sore as well?