Jock itch (tinea cruris) is a fungal infection that causes a red and itchy rash in warm and moist areas of the body. The rash often affects the groin and inner thighs and may be shaped like a ring.

Jock itch gets its name because it's common in athletes. It's also common in people who sweat a lot or who are overweight.

Although often uncomfortable and bothersome, jock itch usually isn't serious. Treatment may involve keeping the groin area clean and dry and applying topical antifungal medications to the affected skin.

Jock itch usually begins with a reddened area of skin in the crease in the groin. It often spreads to the upper thigh in a half-moon shape. The rash may be ring-shaped and bordered with a line of small blisters. It may burn or feel itchy, and the skin may be flaky or scaly.

When to see a doctor

See your doctor if your rash is painful or you develop a fever. And see your doctor if the rash hasn't improved after a week of treatment or if it hasn't cleared up completely after three weeks of treatment.

The organisms that cause jock itch thrive in damp, close environments. Jock itch is caused by a fungus that spreads from person to person or from sharing contaminated towels or clothing. It's often caused by the same fungus that causes athlete's foot. The infection often spreads from the feet to the groin because the fungus can travel on your hands or on a towel.

You're at greater risk of jock itch if you:

• Are male
• Are a teen or young adult
• Wear tight underwear
• Are overweight
• Sweat heavily
• Have a weakened immune system
• Have diabetes

Reduce your risk of jock itch by taking these steps:

• Stay dry. Keep your groin area dry. Dry your genital area and inner thighs thoroughly with a clean towel after showering or exercising. Dry your feet last to avoid spreading athlete's foot fungus to the groin area.
• Wear clean clothes. Change your underwear at least once a day or more often if you sweat a lot. It helps to wear underwear made of cotton or other fabric that breathes and keeps the skin drier. Wash workout clothes after each use.
• Find the correct fit. Make sure your clothes fit correctly, especially underwear, athletic supporters and sports uniforms. Avoid tight-fitting clothes, which can rub and chafe your skin and put you at increased risk of jock itch. Try wearing boxer shorts rather than briefs.
• Don't share personal items. Don't let others use your clothing, towels or other personal items. Don't borrow such items from others.
• Treat or prevent athlete's foot. Control any athlete's foot infection to prevent its spread to the groin. If you spend time in moist public areas, such as a gym shower, wearing sandals will help prevent athlete's foot.

Your doctor can often diagnose jock itch by looking at the rash. If the diagnosis isn't clear-cut, your doctor may take skin scrapings or samples from the infected area for study under a microscope.

For mild jock itch, your doctor may suggest first using an over-the-counter antifungal ointment, lotion, powder or spray. Apply the medication as your doctor recommends for one to two weeks even if the rash clears up quickly.

If you also have athlete's foot, it's usually treated at the same time as jock itch to reduce the risk of the rash coming back. Severe jock itch or a rash that doesn't improve with over-the-counter medicine may need prescription-strength creams, ointments or pills.

Your family doctor or a skin specialist (dermatologist) can diagnose jock itch. Here are some tips to help you get ready for your appointment.

Your time with your doctor may be limited, so preparing a list of questions can help you make the most of your appointment. For jock itch, some basic questions to ask your doctor include:

• What's the most likely cause of my symptoms?
• Are tests needed to confirm the diagnosis?
• What treatments are available?
• Is this condition temporary or long lasting?
• Is there a generic alternative to the medicine you're prescribing?
• What can I do to prevent the infection from spreading?
• What skin care routines do you recommend while the condition heals?

What to expect from your doctor

Your doctor is likely to ask you a number of questions, such as:

• When did you first notice your symptoms?
• What did the rash look like when it first started?
• Have you had this type of rash in the past?
• Is the rash painful or itchy?
• Have you used any medications on it already? If so, what?