Due to constant skin-to-skin contact, infections of the skin are a common and unfortunate part of Jiu-Jitsu. The prevalence of such conditions has changed the way many people look at the sport, and there have been many misconceptions about something that arguably is one of the greatest health concerns among athletes in the 21st century.
The issue is with the lack of education about skin infections, especially in preventing and treating them. The truth is that most types of skin infections in Jiu-Jitsu are extremely minor and only become a major health issue if they are not cared for properly.
The most common types of skin infections in BJJ, Judo and  Wrestling : Ringworm.

About Ringworm

Ringworm (Tinea corporis) is a type of fungal infection that can be contracted almost anywhere on the body. When contracted on the feet, this infection is known as “athlete’s foot.” On the groin area, it’s called “jock itch.” The name is misleading, because there is no actual “worm” involved. One of the most common types of skin infections, ringworm appears on the skin as a raised circle or ring. It is typically red or brown around the edges with scaly, peeling skin throughout.
Ringworm thrives in warm, moist areas and can be contracted from many sources, including but not limited to: Unclean locker rooms, clothing, showers, mats, and of course, skin-to-skin contact with infected individuals. Ringworm can also be found on some animals.
Symptoms:
Ringworm has a very distinctive appearance, and typically appears in the form of a ring-shaped, itchy rash that is slightly raised above the skin that surrounds it. Every case is different, and sometimes it will not appear in this shape and may not be irritating. Sometimes, reddish or brownish bumps appear in addition to scaly, peeling skin. It is also common to contract ringworm in difficult places to view, such as the scalp or underneath the fingernails.
Prevention:
A prescription shampoo or an over-the-counter dandruff shampoo that contains selenium sulfide, such as Selsun Blue® or Head and shoulders will be a great prevention to Ringworm. (The shampoo will help prevent the spread of ringworm, but it will not cure it.). Wrestlers have been showering with dandruff shampoo for years.

Selenium sulfide produces a mild tingling sensation when used in a shampoo. A shampoo containing selenium sulfide is used twice a week for two weeks, then once a week for up to four weeks. It should be kept away from the mouth or nose, and it should not be used if the scalp has inflamed or broken skin. Shampoo with selenium sulfide should be massaged into the scalp, then left on for three minutes. Some brands of this shampoo must be applied twice, then rinsed. When treating tinea versicolor, the shampoo should remain on the skin for 10 minutes before rinsing.
Those using shampoo with selenium sulfide should wash their hands after applying the shampoo. Side effects can include dry skin, oil skin, dry or oily hair, temporary hair loss, or skin irritation. If any side effects occur, the use of the shampoo should be stopped.
Other ingredients used to treat dandruff include coal tar, salicylic acid and zinc pyrithrione as active ingredients. Selenium sulfide can also be applied topically to treat dandruff.

Treatment:
Most cases of ringworm are extremely minor and can be treated with over-the-counter, topical medications that are commonly used for fungal infections. Make sure to follow the directions of any medication exactly. It may take several days to several weeks for the infection to be healed, depending on severity. “Lamisil” is a good cream that works wonders.
Often times, your doctor will be able to identify ringworm with a quick examination of your skin. If your infection is strong, oral antifungal medications may be prescribed in addition to prescription topical medications. After a few days of treatment, ringworm becomes non-contagious, although it is still apparent on the skin. It may take up to several weeks for ringworm to completely disappear.