When my nephew was little he had a red, swollen foreskin / penis and it meant a trip to the doctors then the hospital.
He had an infection that had got in at a weak moment. He had a temp, was weeing heaps and was quite unsettled.
Dr said if if happened again he would have to be circumcised. Never happened again thankfully.

Sometimes the tip of my boys Penis' gets a bit red and sore looking.
I have never put anything on it. A nice long soak in the bath tends to help.

Sorry i am not much help.

xxxoooo