How Can An Allergic Skin Reaction On The Penis Be Treated?

I was circumsized as a child...I am 46. Think I may have an allergic reaction of some sort on my penis. It is on the underside between the head and the shaft on the circumsized foreskin area. There is swelling there. It is internally hardened and has a deep tissue itch to it. There are no surface sores. I had sex a week before symptoms began with a girl I ve been with often over six months...Tuesday night the internal itching began...in the morning there was swelling. By Wednesday it had spread to the sides but now on Thursday it has receded back to its original position. Am I right to hope it is simply an skin irritation or is this venereal,???