Jock itch, also known as tinea cruris, is a fungal infection of the skin in the groin. The warm, moist environment is the perfect place for the fungus to grow. Anything that enhances that environment puts the person at risk of getting jock itch. Therefore, wearing sweaty, wet clothing in the summer time or wearing several layers of clothing in the wintertime causes an increased incidence of jock itch. Men are affected more often than women.
The Jock Itch FungusThe fungus that most commonly causes jock itch is called Trichophyton rubrum. It also causes fungal infections of the toes and body. Under the microscope, this fungus looks like translucent, branching, rod-shaped filaments or hyphae. The width of the hyphae is uniform throughout which helps distinguish it from hair, which tapers at the end. Some hyphae appear to have bubbles within their walls, also distinguishing them from hair. Under most conditions these fungi inhabit only the dead skin cells of the epidermis.
Jock Itch AppearanceThe rash of jock itch starts in the groin fold usually on both sides. If the rash advances, it usually advances down the inner thigh. The advancing edge is redder and more raised than areas that have been infected longer. The advancing edge is usually scaly and very easily distinguished or well demarcated. The skin within the border turns a reddish-brown and loses much of its scale. Jock itch caused by T. rubrum does not involve the scrotum or penis. If those areas are involved, the most likely agent is Candida albicans, the same type of yeast that causes vaginal yeast infections.
Rashes Similar to Jock ItchThere are other rashes of the groin that can cause symptoms similar to jock itch. The first is called intertrigo which is a red, macerated rash at the groin fold not caused by a fungus. It is seen many times in obese patients and caused by moist skin rubbing against moist skin. The skin cracks and breaks down in lines called fissures, which can be very painful. These fissures can get secondarily infected with fungi or bacteria. The edge of the rash usually does not advance until much later in the life of the rash.
The other condition that mimics tinea cruris is called erythrasma. This is a bacterial infection that affects the groin and advances down the inner thigh similar to tinea cruris. However, the rash of erythrasma is flat and more brown than red throughout the affected area. It also does not have any scale or blisters.
Jock Itch DiagnosisThe best way to diagnose tinea cruris is to look for hyphae under the microscope, a KOH test. The skin is scraped with a scalpel or glass slide causing dead skin cells to fall off onto a glass slide. A few drops of Potassium hydroxide (KOH) are added to the slide and the slide is heated for a short time. The KOH dissolves the material binding the skin cells together releasing the hyphae, but it does not distort the cell or the hyphae. Special stains such as Chlorazol Fungal Stain, Swartz Lamkins Fungal Stain, or Parker's blue ink can be used to help visualize the hyphae better.
Jock Itch TreatmentJock itch is best treated with topical creams or ointments since the fungus only affects the top layer of skin. Many of the antifungal medications require a prescription, but there are three that can be bought over-the-counter (OTC). The OTC antifungals are tolnaftate (Tinactin), clotrimazole (Lotrimin), and miconazole (Micatin). Creams used to treat jock itch should be applied twice a day for at least two weeks. Application can be stopped after the rash has been gone for one week. Creams should be applied to the rash and also at least two finger widths beyond the rash. Many people with jock itch also have athlete's foot and these same creams can be applied to the feet. However, treatment of athlete's foot can take up to four weeks. If the rash is very red and itchy, especially if it has blisters at the edge, a topical steroid such as hydrocortisone can be applied also. Steroids should not be used in the groin alone without consulting a health care provider since steroids alone can make the rash of jock itch much worse.
Jock Itch PreventionTo prevent jock itch from occurring or re-occurring, several measures may be taken.
- Wear loose fitting clothing made of cotton or synthetic materials designed to wick moisture away from the surface.
- Avoid sharing clothing and towels or washcloths.
- Allow the groin to dry completely after showering before covering with clothes.
- Antifungal powders or sprays may be used once a day to prevent infection.