Athlete's foot (or tinea pedis) is a fungal infection of the skin on the feet. Fungi tend to grow well in dark, damp, warm places, so the the feet and groin are very common sites of infection. When found in the groin, this infection is called tinea cruris (or, commonly, jock itch). The infection CAN be passed from foot to groin. This can happy by direct contact, or by use of a towel on both regions. Fungal infections could even be spread to other parts of the body that are dark, damp, and warm, such as skin folds (tinea corporis), and, rarely, the scalp (tinea capitis).
To prevent spread of the fungus from one part of the body to another, make sure to use a clean towel at all times, and to dry your infected areas (feet and groin in your case) last, or with a separate towel. To treat and limit the extent of your tinea cruris and tinea pedis, make sure to dry off both areas thoroughly after showering and before putting on socks. You can also use baby powder and other powders to help keep these areas dry. Always use clean socks and underwear. Medically, certain anti-fungal creams are available to help treat these infections, but must be prescribed by your primary care physician
or a dermatologist