Ringworm infection on the groin of a 38 year old male patient. A ringworm (tinea) infection of the groin is known as tinea cruris, or jock itch. Ringworm is a disease caused by a fungal infection of the skin. It can be caused by various fungi, including Microsporum and Trichophyton. It causes severe itching. The disease is highly contagious, and can be spread by direct contact or by contact with contaminated material. Treatment is with antifungal drugs.