Skip to Main Content


A 59-year-old man presents with itching in the groin (Figure 145-1). On examination, he was found to have scaly erythematous plaques in the inguinal area. A KOH preparation was performed with Swartz Lamkins stain, and the dermatophyte was highly visible under the microscope (Figure 145-2). He was treated with a topical antifungal medicine until his tinea cruris resolved.

FIGURE 145-1

Tinea cruris in a 59-year-old Hispanic man present for 1 year. (Reproduced with permission from Richard P. Usatine, MD.)

FIGURE 145-2

Microscopic view of the scraping of the groin in a man with tinea cruris. The hyphae are easy to see under 40× power with Swartz Lamkins stain. (Reproduced with permission from Richard P. Usatine, MD.)


Tinea cruris is a pruritic superficial infection of the groin and adjacent skin caused by a dermatophyte fungus.


Common names: Crotch rot and jock itch.


  • It is estimated that 10% to 20% of the world population is affected by fungal skin infections.1

  • Dermatophytes are the most prevalent agents causing fungal infections of the skin.2

  • Trichophyton rubrum causes the majority of cases of tinea cruris.2

  • Tinea cruris is more common in men than women (threefold) and rare in children.


  • Caused by the dermatophytes Trichophyton rubrum, Epidermophyton floccosum, Trichophyton mentagrophytes, and Trichophyton verrucosum.

  • Can be spread by fomites, such as contaminated towels.

  • The dermatophytes release keratinases, which allow invasion of the cornified cell layer of the epidermis.

  • Autoinoculation can occur from fungus on the feet or hands.


  • Wearing tight-fitting or wet clothing or underwear has traditionally been suggested; however, in a study of Italian soldiers, none of the risk factors analyzed (e.g., hyperhidrosis, swimming pool attendance) were significantly associated with any fungal infection.3

  • Obesity and diabetes mellitus may be risk factors.4



The cardinal features are scale and signs of inflammation. In light-skinned persons inflammation often appears pink or red, and in dark-skinned persons the inflammation often leads to hyperpigmentation (Figures 145-3 and 145-4). Occasionally, tinea cruris may show central sparing with an annular pattern as in Figure 145-5, but most often is homogeneously distributed as in Figures 145-3 and 145-4.

FIGURE 145-3

Tinea cruris and tinea corporis in a Hispanic man with hyperpigmentation secondary to the inflammatory response. KOH positive. (Reproduced with permission from Richard P. Usatine, MD.)

Pop-up div Successfully Displayed

This div only appears when the trigger link is hovered over. Otherwise it is hidden from view.