Jock itch is a dermatophyte (fungal) infection of the groin.
Tinea cruris is a type of dermatophytosis (see see Overview of Dermatophytoses (Ringworm, Tinea)). Tinea cruris is primarily caused by Trichophyton. This infection is much more common among men because moisture can get trapped between the scrotum and thigh. Tinea cruris develops most frequently in warm weather or when wearing wet and tight clothing. People who are obese are at risk because their skinfolds trap moisture.
The infection begins in the skinfolds of the genital area and can spread to the upper inner thighs and may occur on both sides. Usually the scrotum is not affected or is only slightly affected. The rash has a scaly, pink border. Tinea cruris can be quite itchy and may be painful. This infection often recurs, particularly among people who have onychomycosis or tinea pedis, because fungi can spread from those infections to the groin. Flare-ups occur more often during the summer.
The diagnosis is usually obvious to doctors based on a physical examination. Treatment involves an antifungal cream or lotion (such as miconazole, naftifine, ketoconazole, or clotrimazole). Antifungal drugs taken by mouth (such as itraconazole or terbinafine) may be needed in people who have infections that are widespread or cause inflammation or infections that are difficult to heal.
Last full review/revision June 2013 by Denise M Aaron, MD