Jock itch is a fungal infection that produces a red, itchy, ring-shaped rash on your inner thighs, genitals, and buttocks. It is most common in overweight people or those who sweat a lot, but things like too tight underwear, poor hygiene, and sharing of items like towels and razors INCREASE your chances of getting the itch. Treatment is fairly easy. Look for an over-the-counter antifungal medication containing either azoles or allylamines, which are both important compounds that INHIBIT fungal growth.