Why Does My Partner Get A Rash On His Penis After Unprotected Sex, Even Months Postpartum?

Everytime my partner and I have intercouse he gets rashes on his penis. Went to the doc and finished an antibiotic cause that came along with Clotrimazole Vaginal Cream while I was pregnant months ago. It s now 6 months postpartum and had been condomising all along long after the first incident until when we tried again and the rash instantly came out after unprotected intercouse. What can I do?