Jock itch also known as tinea cruris, is a fungal infection of the skin on the groin, upper inner thighs, or buttocks. It most commonly occurs in hot, humid conditions.

Men are affected more often than women and the perfect place for this fungus to grow is warm, moist environment. 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

Trichophyton rubrum is the fungus that most commonly causes jock itch and other 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.

The fungus that causes jock itch most often results from :
Wearing wet, damp, or unlaundered clothing (such as underwear or an athletic supporter)
Sharing towels that are infected with jock itch fungus
Infrequent showering, especially after exercising or perspiring heavily from work
Hot, humid conditions
Heavy perspiration
Obesity
Tight clothing
Re-wearing clothing, especially underwear or athletic supporters, before laundering
Changing underwear infrequently
Using public showers or locker rooms
Immune system disorders

Jock itch causes a chafed, itchy, sometimes painful rash in the groin, upper inner thigh, or buttock. The rash of jock itch starts in the groin fold usually on both sides and advances down the inner thigh. The advancing edge is Red and usually scaly . 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. The rash is:

 Usually red, tan, or brown
 Usually defined clearly at the edges
 Often slightly scaly

Jock 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 products that can be bought over-the-counter (OTC). The OTC antifungals are

 Tolnaftate
 clotrimazole
 miconazole
 Econazole
 Oxiconazole
 Ketoconazole
 Terbinafine
 Ciclopirox
 Haloprogin
 Naftifine
 Undecyclenic

Do not use antifungal creams recommended specifically for athlete's foot. They may be too harsh for the groin. Other creams used to treat jock itch should be applied twice a day; two finger widths beyond the rash 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. 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. Do not use any Sprays.

In severe or persistent cases, your doctor may prescribe stronger creams or oral medication. Use your prescription for the entire time that your doctor recommends. This will help prevent re-occurrence of the rash. If your rash does not resolve within a month of treatment, contact your doctor.

To prevent jock itch from occurring or re-occurring, several measures may be taken.
Shower regularly and soon after exercising or perspiring heavily.
Dry the groin area thoroughly.
Apply absorbent powder after showering to help keep the groin area dry.
Wear loose fitting clothing made of cotton or synthetic materials designed to wick
Moisture away from the surface.
Wear cotton underwear and breathable clothing.
Avoid sharing clothing and towels or washcloths.
Always launder clothing, such as underwear and athletic supporters, before re-wearing.
Allow the groin to dry completely after showering before covering with clothes.
Anti fungal powders or sprays may be used once a day to prevent infection.
Do not store damp clothing in your locker or gym bag