Thanks for contacting HCM I am sorry to hear that you are having a rash in your groin. This sounds very much like a fungal infection or something called jock itch. It is caused by a fungal growth in the groin where fungus likes t grow in warm dark and moist areas. In my practice I see this often and treat it with antifungal powders like Tinactin or Lamisil. To help prevent the rash be sure to shower and dry off completely after exercise. Wearing less restrictive clothing like boxers may also help reduce the infection and irritation. Hope this answers your question. Please contact us again with your medical questions or concerns