Jock itch or Tinea Cruris is not a yeast infection, but it is caused by a fungus. Tinea Cruris infections can affect the scrotum, groin and penis. It is commonly caused by other fungal infections i.e. athlete’s foot spreading to the area, but tight-clothing, hot and humid conditions and a compromised immune system can increase your risk of infection. The Trichophton rubrum fungus is responsible for 90% of cases and can be treated by antifungal medications known as azoles and allylamines.